Are you sure there's no adjustment ? Many modern monitors have a skew adjustment in software, that allows the picture to be rotated electronically. You can also get what looks like a twisted picture, if the top/bottom and sides trapezium/ parallelogram adjustments are both out.
The Dell monitor that I'm using right now, has no less than 11 'soft' adjustments for raster geometry, including width, height, v.shift, h.shift, rotation, side pincushion, side pincushion offset, trapezium, parallelogram, top corner flickout and bottom corner flickout. Between all of these, it is possible to get the picture near as dammit, perfect. I'd be surprised if your monitors hadn't got a similar set of adjustments.
Failing that, assuming you are saying that the picture is rotated, rather than distorted, it's a case of slackening the deflection yoke clamp, and rotating the whole assembly slightly. However, you might want to take care if you do this, and consider whether the level of error that you have, is worth the trouble, as rotating the yoke can be difficult if the rubber wedges have been silicon rubbered to the CRT bowl, and may lead to compromised purity and corner convergence anyway.
Arfa