what is the service fee per reservation?

I would imagine that information would show up on the bill when you book with a sitter. You should see it as a separate line item I would think.

Rover doesn't give any specifics on how it is calculated, only that it cannot exceed $50:

https://support.rover.com/hc/en-us/arti…

I suggest you call Rover Customer Support to see if they can give you more detail other than what I posted. The number is [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team]. Your potential sitter would have no idea of how it is calculated either or ability to change it.