If you are looking for some old RTS game that differs from most games in the same genre, Praetorians is probably what you are looking for. The game was made and released back in 2003 by Pyro Studios and Eidos Interactive.
It is a different RTS game. As soon as you start it, you'll notice that there are no resources to micromanage. The only "resources" in the game are your troops. They can be purchased when you capture new settlements/villages. And, the more they fight (and survive, of course), the better they become. Think of it like some sort of an experience-gaining auto-upgrade system.
The game features three single-player campaigns and also multiplayer. You can play as the Romans, the Barbarians or the Egyptians. The missions are fun and can be at times a little hard for some players that are well into the RTS genre.
I don't know if the GOG version has them, but few unofficial patches have been released that fix bugs left in the game. You can search for them on the net, they should still be available for download somewhere.