rotate frame for polygon lasso tool

Let me explain my post.  I am working on a high resolution schematic map containing solid block figures of buildings.  The map is oriented with North directly up.  The high resolution version was started by blowing up a lower resolution version, so the edges of objects like buildings have feathering noise due to the pixel interpolation process.  I'm cleaning up the edges so they will be crisp in the high resolution version by selecting the building, painting the interior of the building one uniform color, inverting the selection, and the painting the exterior a different uniform color.  Buildings generally have borders which are at 90 degree angles, so if the building is oriented N-E-S-W the polygon selection tool with the shift key held down does a very good job of cleanly selecting the edges for this process with enforced right angles between them.  However, if the building is off the N-E-S-W orientation, I can still click on corners with the polygon tool without the shift key, but I can't assure 90 degree angles between them.  I'm asking whether there is a way to enforce the limitaion of lines to be 90 or 45 degrees to each other that the shift key provides, but have the lines oriented at an angle other than 90 degrees to the edges of the image.  Hope that's clearer.