Can I put a metal safe weighing 2000 lbs in a 12x12 room?
If we assume your room was built to minimum standards from the IBC 2015, for example the live load table #1607.1 from here which lists habitable sleeping areas to support 30 pounds per square foot minimum:

(80" x 60" ) /144" = 33.33333 square feet.
so 30 pounds spread over 33.3333 square feet would be 1,000 pounds.

Depends on how over the minimum the original construction was designed to, but would need to be at least 60 PSF to for a 2,000 pounds load concentrated over a 60"x80" area.

Over a 12' span, you would need to have at least 2x8s installed at 16" on center to support 60 PSF.