Really what makes Islamic empire more tolerant than Roman?
Their tolerance for non-Muslims. Romans were barbarians and didn't tolerate anything...persecuted Christianity...and almost completely annihilated Judaism/Jews.
Islamic Civilization was way more tolerant, accepting, and multi-cultural than anything the world had ever seen. Historically, historians agree that Islam was the first-ever "global civilization" of human race (Google the words : The First global civilization).
Infact, scholars of Jewish studies have argued that if it wasn't for Islam, Judaism would have become "extinct" by now due to Western (read Roman) persecution, destruction, and so on.
So, what did the Muslims do for the Jews? | The Jewish Chronicle
Take this for example. This Islamic Empire was the largest-ever human created empire uptil that point in history. Way larger and global than Roman, Greek, or any other local Western empires.
The catch? At its peak, this Islamic-empire was majority
non-Muslim. Whether military, or administration, bureaucracy, or even courts...*majority* of the people working in all these institutions were non-Muslims.
Throughout history, minorities in Islamic World had their own legal system/courts and were allowed to do their own thing independent of state-laws.
History isn't your top strengths, it seems.