The Rocket filter is Air Driven. Even if Shrimp get in the slots, past the Lava Rock Rubble, into the Tube and on the filter floss they will be fine. They could even ride the bubbles out and not be harmed. on'y time you might have to worry is when Changing the filter floss. I find RCS in my Canister filter all the time when I clean it.
Yup, should be fine as stated above, I also find a large colony of shrimp every time I clean my canisters!