I think the Eastern Roman Empire could've held them off though, but for the neglect of the frontier defenses and the army in general in the 11th century.
In the 12th century, the Comneni emperors recovered a lot of Anatolia, and maybe could've gotten back to the old Taurus/Anti-Taurus defense line if Manuel had concentrated there instead of Europe.
The Byzantines might have been better off coming to terms with and allying with the incoming Turks, who had picked up on classical Greek and Roman learning while they were still wandering around Central Asia and Iran. They might have made good allies, certainly better allies than enemies. Ah well.