Return to the Roots has an active IRC channel. It is easy to join this channel using Freenode Web IRC: just give a short nickname (no spaces!), type #siedler2.5 as the channel and you’re ready to connect!
Note that most speak German on the channel, but English is not forbidden! You can ask questions on both original The Settlers II as well as Return to the Roots. Note that RttR supports multiplayer so you can also ask people for a game!