Since, due to Rome’s heavy traffic, it is very difficult to enter the Eternal City driving a bus, most international and interlocal bus companies have their stations far away from the center of town, usually near smaller underground or train stations.
Until not too long ago the only international bus company working from Rome was Eurolines. They have however stopped working in most of Italy. Their position has been taken over by the Flixbus company, which has an extensive network all over Europe.
Flixbus have their base at the Largo Guido Mazzoni, outside Tiburtina Railway Station. Tiburtina can be easily reached by taking metro line B from Roma Termini (4 stops). Their buses are equipped with wifi and plug sockets.
At the moment (December 2017) they provide direct connections to Basel, Bratislava, Frankfurt, Innsbruck, Karlsruhe, Klagenfurt, Ljubljana, Luzern, Lyon, Mannhein, Munich, Paris, Stuttgart, Vienna, Villach, Zagreb and Zurich.