itch.io

This is a wall of text, sorry about that x3

The rooms aren't GameMaker rooms, everything is created in a single room using the data in the room-sprites. It shouldn't be impossible to get premade rooms working, though... the two main scripts you should look into are dungen_render_room() and dungen_spawn_contents() for actually creating room contents. (Specifically the code block with the "If inside the room, we need to actually look up what tile type to spawn." comment... remove that, and then add code after the loop to create the stuff from the premade room.)

This is assuming you want to replace the sprite-sampler system with your own premade room system... if it's for what's commonly called "vaults" (occasional handmade rooms to spice up the randomness) you could add them to dungen_init_specials_list (although that still uses the sprite-based approach) and adding a new sprite to dungen_rooms_assign_biomes for it.

Another thing you could check out for a place to insert your code is dungen_rooms_spawn, once you read rrr you could check global.dungeon_room_type[rrr] to see if you've got a room of a special type, and then spawn it in a different way. (Don't forget to add walls and doors, since _render_room does that too).

I've not thought too much about HOW to make those premade rooms, but there's two easy options. In Studio 1 rooms are XML files, so you could make the rooms in the room editor, copy the files to included files, and then just parse the XML from them.

In GMS2 they're JSON files that don't contain the object names, so that's a bit trickier. I'd go with a bit more involved approach: get into the room, have the creation code of an "room exporter" object run something like

var s = "";
var nl = "
";
with(all){
  if(id != other.id){
    s += instance_create(string(x) + " + xxxx," + string(y) + " + yyyy," + object_get_name(object_index)) + ";" + nl;
  }
};
clipboard_set_text(s);
show_message("Level copied to clipboard!")

Bam, now you have your clipboard filled with a GML script that creates all those instances. Paste it in a new script in your game, and then when you wanna create that room in a dungeon, call it. Just set the variables "xxxx" and "yyyy" to the room's top-left corner coordinates in the new dungeon.