Will Roalesk, Apex Hybrid, trigger Sharktocrab twice?
Yes, it would.
Even though no one gets priority in between the instructions &quot;proliferate&quot; and &quot;then proliferate again&quot;; each instruction is still a separate instance, and Sharktocrab's ability will trigger after each of them.
Abilities trigger as soon as the relevant event happens; they don't wait to trigger until an entire ability is done resolving.

603.2. Whenever a game event or game state matches a triggered ability’s trigger event, that ability automatically triggers. The ability doesn’t do anything at this point.
603.3. Once an ability has triggered, its controller puts it on the stack as an object that’s not a card the next time a player would receive priority.