I seriously doubt that there will be a scripting command like this in TCB:
Create (roach) at 1, 1
But I don't really think that anyone would like unlimited monsters anyways... (roach queens / mothers aren't really unlimited, but they're as close as you can get.)
I think you want monsters appearing when you get in certain areas, right? Then do this:
Q = roach queen
. = empty
W = wall
X = target area
Y = yellow door
WWWWWWWWWWWW
WQQQQQQQQQQW
WQ.........W
WQ.WWW WWW.W
WQ.WQQQQQQ.W
WQ.WQ......W
WQ.WQ. WWW.W
WQ.WQ.WQQQ.W
WQ.WQ.WQ...W
W..........W
WWWWWYWWWWWW
............
............
............
....XXX.....
....XXX.....
....XXX.....
............
When Beethro steps on a square of the target area, the yellow door opens. When he steps off, it closes. Since more than 30 roaches are produced, there will always be one to come out.
Of course, there are 3 errors in my diagram: way to kill, roaches don't all have a clear path, and you need to put force arrows under the queens to keep them there.