T and CT spawns are surrounded by a teleport, sending them to the first room at beginning of the round. There, a trigger_once activates a trigger_changetarget which alters the spawn destination to a new room for next round(and repeat for each round). Schlump's above method resets one trigger_hurt and weaponstrip, which all the rooms share.
Added trigger_hurt and increased the water speed, so you can see the effect faster.
There are 5 rooms(00-04) that cover the first 5 rounds; copy and paste additional rooms for more rounds.
Load the map by using New Game from the CS menu. (WILL NOT WORK loading straight from the console)
The text primitives MAY NOT compile correctly without a HLFix-enabled Hammer, or using Sledge, since I also scaled and skewed them afterwards..