1. Select the Pick tool, and while holding down the SHIFT-key, click on the desired guidelines.
2. Release mouse button and double-click on any of the guidelines
3. Click anywhere on the line (or handles) and perform the rotation.

Note: Although only one guideline is marked with ‘center point’ and ‘curved arrows’ all them will be rotated at same angle. This works for horizontal and/or vertical guidelines.

Tip provided by Silvio Gomes, CorelDRAW Master, Artist and Graphic Designer.