ShadowCollector
[09] Warrior
To elaborate on what LostProvidence said, Rock's approach is fundamentally opposite to Astaroth. Astaroth's movelist is primarily designed to keep the opponent away and fight them at a range. Rock's is just the opposite. Rock wants to stay right in the opponent's face micing them up with grabs, KND's and ground throws. If you try to play Rock as a poor man's Astaroth, you're gonna struggle. You should drop by Rock's soul arena sometime. I'm sure myself and a few others would be more than happy to break down his game in detail there.
I actually like playing Rock more than Astaroth. I like how hard it takes to get decent results with him compared to Astaroth and I love ground grabs ^_^ (If the opponent is an idiot who can't break.)
However fundamentally jonny you can see some similarities in quite a few moves they share. And Yes I'm talking about 6k and 1a. Now before I get flamed for mentioning those two moves, there's also A+B, 4A+B, and the similar bullrush (Rock is CR 3k, Astaroth is 66k). Although I'm not surprise the two are the same because Astaroth as a character in general was based off Rock so it reflects in gameplay.
Sure Rock can be more brutal up close but looking at the two. They ARE similar to a degree. Never said you can play Rock Like Astaroth and Vice-Versa, But it's easier to transfer between the two then let's say Talim and Setsuka.