In Chinese real-estate listings
居室 is the standard count word for bedrooms:
一居室 (1BR),
两居室 (2BR),
三居室 (3BR). The full description usually pairs it with bathrooms and living rooms — e.g.
三室两厅一卫 (3 bedrooms, 2 living rooms, 1 bathroom). For a generic "room" in everyday speech,
房间 (fángjiān) is more common.