Can I re-use a roller tray liner?
There is a good chance that you will be perfectly fine. I've rolled out of trays I've let paint dry in with perfectly fine results when I got lazy and it was an area I wasn't concerned about (like a shed, inside of my garage, etc...)

However, based on which paint you chose, I'd say this is more important area, so why risk it?

There is a chance that the new wet paint plus the bending, flexing, or pressure of you rolling could loosen up some more pieces/flakes.

Liners are cheap, but if you really do plan on reusing them clean them up immediately after use to make it easier.