So I feel accomplished.

It still isn't finished (there are no enemies yet, and the floor layout isn't randomized yet), but I have got the item pickups working, and the rooms are randomized. Doors appear when there's a room adjacent to the one currently occupied. When you go into a door, the room in that direction is randomly chosen from a list of 5 room designs, but then when you leave and reenter it doesn't randomize again.

Things are going pretty well.