Set spawn locations within a random initial spawn room?

Hey guys, so the deal is I have an array of rooms each has its own spawnpoint in the level. At start a random room is selected from the array. Each room also has a set of item spawn points. How do I after a room is chosen from the array then limit where the items can be spawned, as just having an array of all the item spawn locations won't work since they would just spawn outside of the select spawn room from the initial array of rooms. I hope this makes sense any help would be appreciated.