The Perennial Struggle
The perennial struggle of the Jewish nation originated with the struggle our forefather Jacob had with his brother Esau even before they were born.
The Torah relates how Rivkah experienced severe pain in her pregnancy and sought G‑d’s counsel. She was told that she would give birth to twins, and that they would be the fathers of rival nations. Even at the moment of their birth there were signs of a struggle for supremacy:
“And the first one emerged… and they named him Esau. And afterwards, his brother emerged, and his hand was grasping Esau’s heel, and he named him Jacob.”
Jacob, our Sages tell us, was attempting to hold Esau back so he could be the first born. Esau ultimately sold his birthright to Jacob, which he bitterly regretted later when Jacob “deceived” his father into giving him the blessings.
A Blank Piece of Paper
The Midrash relates how a certain Roman official asked the Sage Rabbi Yehoshua, “Who will seize the reins of government after us?” Rabbi Yehoshua took a blank piece of paper and wrote: “and his hand was grasping Esau’s heel.”
Rabbi Yehoshua’s gesture was a not so subtle way of suggesting that the Jewish nation would prevail in the end over Esau and his Roman heirs. Rabbi Yehoshua was referring to the Messianic Age, when all nations of the world will recognize the sovereignty of Moshiach, and witness him usher in an age of universal peace.
The question, however, is why did Rabbi Yehoshua write this message down?  Couldn’t he have stated that answer orally? If Rabbi Yehoshua was afraid to provoke the Roman official by speaking words, he certainly could not have expected to provoke him less by putting this powerful message in writing. Writing those words was not a subtle way of declaring the downfall of the Roman Empire!
Moreover, once the message was committed to writing there was a real danger that it might be seen by more hostile Roman leaders, notorious for their barbaric cruelty towards the Jews, particularly when there was hint of Jewish rebellion.
We also have to understand why the Midrash mentions the fact that Rabbi Yehoshua took a blank piece of paper. What difference did it make whether the paper had some extraneous writing on it or it was totally blank?
Messianic Age: Writing on an Erasure or on a Clean Slate
The following is based on the Chassidic work Arugas Habosem:
The Romans knew that the Jewish nation and its values would ultimately prevail and triumph over Rome and its value system. They were well aware of the eschatological Biblical predictions of the ultimate Messianic Redemption. That alone did not disturb them because their focus was not on the future but on the here and now. However, they were curious to know whether the triumph of Jewish values would be a total repudiation of Roman values or would traces of Rome survive and even contribute to Messianic utopia.
By taking a blank sheet of paper, Rabbi Yehoshua intimated that the Messianic Age will represent a total departure from Roman culture and values. Moshiach will inaugurate a world wiped clean of the Roman’s imprimatur. Moshiach will write the story of life on a clean slate.
Ethics of the Fathers discusses the difference between a person who studied in his youth and one who began studying in old age.  The analogy it draws is a comparison between writing on a blank sheet of paper versus writing over the erasure of earlier writing. In the latter instance a trace of the erased writing will interfere with and muddle the new.
Similarly, Arugas Habosem argues, Moshiach will not merely erase the “writing” of Rome. Moshiach will begin anew, writing on a completely new sheet of paper with no trace of the past.
On the surface, this explanation appears to contradict the Rebbe’s well-known message that Moshiach will not negate the positive features of exile. Moshiach will embrace the positive elements of exile and “merely” insert an aleph, which stands for Alufo shel Olam - the Master of the world, into the word and concept of Golah-exile.  In so doing, Moshiach will transform the word and the world of Golah-exile into Geulah-Redemption. The sole difference between the words Golah and Geulah is the modifying letter Aleph. All of our positive accomplishments will remain intact.
The Rebbe describes three specific dimensions of the inserted Aleph, which represent three stages of development:
The first change, represented by the simple meaning of the Aleph as Master, is our appreciation for G‑d’s role in everything we do. The world’s people will recognize how G‑d is invested in every aspect of their lives. By inserting the Aleph and sparking recognition of G‑d’s role and value in everything, the retained positive features will be greatly enhanced. It is the obfuscating character of exile that does not allow us to truly and fully appreciate and enjoy its positive elements.
The next stage will be the insertion of G‑d’s “mindset.” The Rebbe based this on the alternate meaning of the word Aleph, which is knowledge. In the present Galus era, we possess a limited ability to comprehend G‑d’s intellect. Only G‑d’s “emotions” are evident in the world. We see G‑d’s love and compassion just as we see His anger and judgment. We don’t see the rationale behind everything. That will change in the Messianic Age. We will be exposed to G‑d’s way of “thinking,” as it were. Again, this will not repudiate the past, but profoundly enhance it.
The third stage will represent insertion and realization of G‑d’s transcendent dimension going beyond even His intellect. This too is related to the word Aleph, which when rearranged spells peleh, meaning wonder. We will experience the most sublime divine revelation, but it will manifest itself within the parameters of our previous Galus existence. There will be no abrupt change from or rejection of past qualities and achievements.
How can we reconcile this approach with the thesis that Rabbi Yeshoshua’s writing about the triumph of Jacob on blank paper signaled the belief that Moshiach represents a totally new slate.
Old World; New Mindset
In truth, there is no contradiction. When Rabbi Yehoshua was repudiating Rome, and by extension the Western civilization that succeeded Rome in dominating the world, he was not referring to their positive contributions. It was the mindset of these societies that will disappear forever.
What is it about the mindset of Rome that Rabbi Yehoshua found so troubling? 
The answer can be found in a Talmudic story telling of the reaction of the Sage Rabbi Shimon bar Yochai to the suggestion that Rome should be given some credit for its building of roads and bridges, etc.: “They do it for their own selfish glory.” Rabbi Shimon’s words eventually reached the ears of Roman officials and he was sentenced to death. For the next 13 years he was forced to hide in a cave until the coast was clear.
Rome embodied the heretical approach to life where the person who enjoys G‑d’s abundant blessing exclaims: “My strength and the might of my hand have accumulated this wealth for me.” The bridges and roads the Romans built, along with all the other positive accomplishments of Western Civilization, will endure in the Messianic Age.  No trace of the arrogant and heretical attitude associated with Rome and its heirs could and will survive. Simply erasing and writing over that mindset will not suffice. Moshiach will introduce a totally new and refreshing way to look at the world and our own lives. When we insert the Aleph—in all of its incarnations—into Golah we are not simply adding a letter. Rather, we are afforded an opportunity to see the past in a totally different and novel fashion; we see the world from G‑d’s perspective, the way He created it in the beginning prior to the intrusion of alien ideas.
So while all the positives of our lives in exile will remain, the perspective by which we view these positives will represent a total departure from the past. We will see the world as it was when it was indeed a clean slate, prior to all the messy and distorted “writing” superimposed on it. 
Two Scenarios
An alternate way of reconciling these two visions of the future—whether it will be a clean slate or incremental changes that retain the past—is by referring to a dispute in the Talmud between Rabbi Yehoshua and Rabbi Eliezer. They argued as to which month is the most opportune time for Moshiach to come. According to Rabbi Yehoshua it must be the miraculous month of Nissan, whereas Rabbi Eliezer maintained that it would be Tishrei, the month associated with creation and nature.
It has been suggested that these two opinions principally differ on whether the Messianic Age will come in a natural way or will be punctuated with miracles.
Rabbi Yehoshua held that Moshiach’s coming would be associated with Nissan, the month in which we celebrate Pesach and its many miracles.  He championed the idea that the future Redemption too, will be of a supernatural order. Hence, Rabbi Yehoshua was correct in asserting that no trace of Rome (read: the natural order associated with the period of Galus and Rome) will be left. A totally new world order will emerge.
According to the dissenting view, which Maimonides embraces, the Messianic Age will occur in a natural order, therefore Galus conditions will not be repudiated. Instead, they will be enhanced and illuminated. 
Whichever way G‑d chooses to bring the Final Redemption, our heartfelt prayer to Him is bring it now, we are ready!