Okay, this might not be the answer you're looking for, but rape is against will, and I've had "rape-like" fantasies, but in the fantasies I'm the one being forced into it, and I've yet to find my self thinking about raping someone else. Not that i think it's wrong. There's a few points to be made about this.
If you're thinking about it to the point where you want to rape someone, and you're honestly worried about your self control, than you need to go seek help with that.
If you're fantasizing about it, when you get done, and that's the end of it, than that's perfectly fine. Even when people fantasize about forcing someone to have sex with them, and violently beating them, i think (personally) it's okay.
But if you think about doing that in real life, for even a split second, than it becomes wrong, and you have a problem. And it's not even your fault, so don't be scared to get help about it either.
And again, if it's purely fantasy, than go for it. That's the best part about fantasy, you can fantasize about ANYTHING, the real world doesn't matter, it's just important you tell the two apart lol.