Secondly, roleplaying means an avatar (persona actually), not a fictional character, so don't worry how them not "roleplaying" because they prefer combat or don't talk "in character". "Out of character" combat is roleplaying too.
Well, if you are going to pull up a Wikipedia page that's specifically about psychology for support, I'll pull up the Wikipedia page on Roleplaying:
"In roleplaying, participants adopt and act out the role of characters, or parts, that may have personalities, motivations, and backgrounds different from their own. Roleplaying, also known as RP to some, is like being in an improvisational drama or free-form theater, in which the participants are the actors who are playing parts, and the audience...."
It then goes on to reference psychology, but is not limited to the psych definition.
Which is not to say that choices in combat don't constitute roleplaying. But please don't expect us to limit our definitions to what the psych people use. Whether or not our games are theatre, they aren't formal counseling sessions, either. The psych definitions do not apply.