@goodgame
For a more serious reply: As already stated CORPS is good in this regard, but are also playing strategic games.
Now for my suggestions in order(1 is the best to join and so on).
1.CORP
2.Stahlgewittern
https://www.warzone.com/Clans/?ID=84 (as a semi role-player myself i gotta suggest this clan they are a great bunch of people, there as some good ones stopped playing recently but the one renaming should still be fire and ready for some new blood--> ived played a lot with guys from this clan)(ps. this clan is always looking for members to add to their regular role-play diplo games).
3.The Roleplayers Guild
https://www.warzone.com/Clans/?ID=3 (i only belive they are roleplaying, but havent played that much with em, i belive they have more clan only role-play games).
4.Nuke Diplomacy
https://www.warzone.com/Clans/?ID=372 (they are currently playing in CL meaning strategic leuge basicly, but i belive they are role-players too. They have had some bootes lately, but they are few, so might be worth a shot).
5. Roleplayers Realm
https://www.warzone.com/Clans/?ID=68 (there are pretty many of them, unknown who many actually plays i dont know rly).
6.The Last Alliance
https://www.warzone.com/Clans/?ID=349 (this is a newer role-play clan maybe they are more active, than no.5? whos from 2013?).
Well there you got it, they ones i know have been known by most, but again no.1, 2, 3 are the best options really. Good luck, hunting role-players!