Depends on the dragon and the home. You want it to be big enough not to get lost or be able to get into places that are not accessible.
I live in a old house with build in heater vents, the spacing is wide, no way I could ever let a baby or juvenile roam. Now that sam is big enough his head won't fit between the vents, he can finally get out.
Any roaming he has done in the past was leashed