You can rotate any text, layer or a selected area on the canvas by following these steps:
Use any of the selection tools to select part of your canvas. If you want to rotate entire text or layer, skip this step.
Switch to the Transform tool (Shift+T)
Move your cursor just outside of a corner of the selection box, click and drag the cursor clockwise or anti-clockwise - the object will rotate
The Transform tool also has additional settings that might be helpful such as vertical or horizontal flipping. Read more in the Transform tool guide.