@Mike has a wonderful answer that attaches the seven seals to events in Rome up until the 400's. My view (shared by others) is that history is fractal and that the grosser features of Revelation have been repeated multiple times, with one ultimate fulfillment yet to come that will match all the details perfectly. This makes all of history a series of warnings to the inhabitants of the earth, threatening a great judgment if they do not repent.
Judgment of Byzantium
A second application of the seals would be against Byzantium.
First seal and first horseman (who wielded a bow): Mohammed, who was an Arab descended from Ishmael, noted as an archer in Genesis. When Mohammed captured Mecca, he removed the idols from the Kaaba. The Kaaba also contained seven arrows used for divination.
Second seal and second horseman: Civil war. The Byzantine empire was gripped by civil war for centuries.
Third seal and third horseman: Pestilence. The Great Famine of the early 14th century was followed by the Black Plague.
Fourth seal and fourth horseman: Death. This includes the Black Death, which returned about a dozen times to Constantinople over the course of a century, and concludes with the Ottoman conquest and fall of Constantinople in 1453 AD.
Fifth seal: Persecution. After Constantinople fell, millions of Christians in Asia Minor and the Balkans were killed, enslaved or forcibly converted to Islam.
Sixth seal: Earthquake. The whole political structure of Europe was transformed.
Seventh seal: Silence. The silence was waiting for what God would do next.
Discipline of the Church
Another application of the pattern is God's judgment upon the church, not to destroy her, but to perfect her.
First seal and first horseman: Ottoman conquest of Byzantium (the Ottomans were the successors to Mohammed, hence inheritor of his bow). In this pattern the consummation of the previous judgment is the starting point for this new series. This is a judgment against relying upon a unified state as savior. Purpose: Political freedom.
Second seal and second horseman: Civil war inside the church. The Protestant Reformation and wars of religion of the 16th and 17th centuries. This was judgment against relying upon a single church hierarchy as a savior. Purpose: Religious freedom.
Third seal and third horseman: Pestilence. The Industrial revolution and advent of capitalism caused the deaths of millions, as increased productivity in the industrializing nations lowered prices and impoverished traditional peoples. this also included the anti-slavery movement. The old economic order was completely overturned. Purpose: Economic freedom.
Fourth seal and fourth horseman: Death. Nationalism, Classism and Racism opposed by unifying ideologies like Democracy and Communism, leading to the horrendous wars and revolutions of the 20th century. Purpose: Equality.
Fifth seal: Persecution. This is the next seal to be opened. A fresh wave of persecution will usher in Solomon's "a time to hate". Hate has to do with choosing for and against, with taking sides. The end of the world will see the sheep and goats separated into two camps. We are currently seeing deep fractures forming in our society. They will widen, until true Christians, Jews and lovers of God will be partitioned from the rest of society.
Sixth seal: Earthquake. This will be the final war against Leviathan. Within this larger structure of the discipline of the church will occur a new instance of the fractal pattern of seven seals. This last fractal will be judgment against the whole world, not just Rome, Byzantium or the church. Unlike the discipline of the church, which led to civilizational advance and the promotion of Christian ideals throughout the world, the final set of seven seals will destroy the world to make a place for the heavenly city to descend.
Seventh seal: Silence. This silence will be concurrent with the peace of Christ's final victory in the final set of seals. In the silence, the seventh trumpet will sound.