Veteran, Pathfinder player since 2010 and have played many other systems in that time.
This is a question many GM's and players like answered, and for most it will come down to the latter. For me, it's about a hierarchy. I as a gamer am first and foremost interested in mechanics. How they work, how they can be mixed to do new things, etc. In that sense, I am a "roll" player. But the reason I like mechanics isn't because I enjoy exploiting them. In fact, 9/10 I inhibit my characters because of sub-optimal builds since I enjoy the flavor inherent in mechanical mixing and multiclassing. Yes, I am a habitual multiclasser because I crave stacking and intermixing abilities to accomplish something that is flavorfull and enjoyable within the game's rules.
So, in that respect, the mechanics are a means to an end when it comes to "role". They give me guidance and inspiration. Probably more than needed for that but wanted to get that out of the way. I won't be munchkining my characters, I don't believe in that. I am mostly concerned with making a character that doesn't hold the party back mechanically (I have done that many times).
First off, my favorite class is Fighter cause it meshes best with my playstyle. I am obsessed with feats, and really enjoy martial prowess from a character standpoint. That being said, I also enjoy rogue-types and casters depending on the role I want to portray. In fact, one of my absolute favorite classes is Witch, followed closely by the Arcane Trickster prestige. Magus is a close third. I love magic, but it just doesn't flow as fluidly for me so generally I avoid full casters. But I can work with any role in any party.
Personally I dislike homebrew, because it adds elements to the game that are either unpredictable or unbalanced (be it overpowered or underpowered). I will not outright reject it if the reasoning is sound and the rules make sense. But I have had GM's that change rules becuase as a player they felt certain things deserved to be more powerful. One GM I decided not to play with houseruled everything that applied to a Paladin to make them hands down the best class in the game. I don't enjoy that, or the changing of some fundamental rules because I feel it both undermines the intentions of those who created the game as well as doesn't really add any new substance (most of the time). 90% of roleplaying is done without dice unless they are absolutely needed, and combat is something that's very easy to break for better or worse when you start fiddling with the fundamentals of the mechanics