In the series of YAUP another useless plugin under a motto:
"Sometimes even simple things are hard to do."
With a little CAD could be more easy.
It could be found under Tools and on tool bar as a pentagon icon.
This plugin generate a regular room between 3 to 30 sides.
You have to input the sides number, the length of the side and the room center position.
It look like this:
Also on Source Forge.