I cant find any fresh water shrimp called "rock shrimp" as a common name, its rostrum looks very similar to amano or bamboo shrimp. Its very hard to see from the picture but does the shrimp have filter nets like bamboo shrimp do, or does it have small nippers like amano shrimp do?
I believe the shrimp in your photo might be called a Mountain Rock Shrimp, but from the quick searches I have done for information on them there isn't much available.
If it is the species I think it is then it probably wont be able to breed successfully in fresh water, their young have a brackish stage in their early life cycle, they should be pretty fish safe but I cant guarantee that they would never predate on the odd small fry.