Originally Posted by Fat Deck Knight
Rohpushin's greatest problem will be differentiating itself from Machamp. Machamp is only slightly less powerful, but it's similarly bulky and faster.
The only thing that Machamp really carries as an advantage is No Guard and Dynamicpunch. Stone Edge is slightly irrelevant since Rock Slide, of all moves, can be boosted to have +20 base power in exchange for flinching (which who cares). Machamp's Spe is barely an edge: at best it does a Speed creep with Blissey. At the moment, Sleep Talk also remains an advantage. I'll grant you that Confusion is a huge boon.
Meanwhile, Rohpushin carries edges with Encourage boosting its Rock-type attacks. Guts is easy to use on this guy, unlike Machamp since under most circumstances Machamp needs to fire No Guard Dynamicpunches to make sure the opponent has a 50% chance of doing nothing. Mach Punch is also significant as it gives Rohpushin a STAB priority move as well.
Defensively, Machamp has a max HP of 384 with 196 Def | 206 SpD, since we're assuming max Atk. 0 EV Rohpushin has 351 HP: a difference of 33 points I admit, but Machamp also put all of its EVs into HP while Rohpushin hasn't invested a single point. For its other Defenses it has 226 Def | 116 SpD. Assuming max Atk, X-Act's Defensive Applet suggests 381 HP | 226 Def | 199 SpD.
Still, defensively they're about even, though Rohpushin leads more physically defensive while Machamp has a little more Special Defense on him.
Either way, yes, it does have to find some niches away from Machamp, but you have to admit: it does already have some with the base stats and a few key differences in the movepool. Machamp can't even brag Iron Fist Focus Punch, but of course in return Rohpushin can't counter No Guard Dynamicpunch easy.
If I'm to understand Encourage correctly, Brick Break would actually be its most powerful STAB, (at 112.5 in exchange for not breaking screens, and much better PP than Drain Punch), and should be used over Hammer Arm (since Encourage does not stop stat drops and BB would have more accuracy). This would need to be tested though.
I was unsure on it, so I didn't list Brick Break. If you're right, though, then yeah I can easily see Brick Break as the best STAB since it has 150 base power (with STAB and Encourage boost included).