Predefined rooms can be accidentally glued together. These predefined rooms are stored somewhere and used by the generator when generating.
This engine uses predefined room layouts, room maps are stored in bitmaps so you can quickly draw new rooms using Game Maker's sprite editor. There's also separate sprites for normal rooms, boss rooms, player start rooms and treasure rooms, so you can easily have some layouts only be used in some contexts, and this system probably wouldn't be too hard to extend either (e.g. you could randomly change some rooms' layouts to layouts from your "SPECIAL STICK ROOM" if you want 2-3 stick rooms in the middle of all the normal ones).
i need one big room, and this room is generated of any room "parts" and stick together...
Everything is still placed in a single GM room... the view scrolling effect is just there because the generator is inspired by Binding of Isaac, if you remove it and have the view follow the player normally it becomes a single cohesive room.