Quickleaf
Legend
DM question for ya.
If the party does a short 1 hour rest in a dungeon room they just cleared, can it be interrupted? if so what percent of the time should I interrupt it as a DM?
Not enough information.
If by cleared you mean "killed all monsters and there's no chance of random encounters anymore", then logically they should be able to rest without interruption.
Playtest rules gave these guidelines for frequency of random encounters:
Mostly uninhibited 20 /d20
Typical dungeon 18-20 /d20
Densely inhabited 16-20 /d20