You can either use the arrow keys and home/end keys on your keyboard, here is a list of all shortcut keys, https://www.mecabricks.com/en/forum/topic/10

Or you can press M key the change to rotation gizmo and click/drag on the circles around the part.

Or:

• Use the keyboard combination: R + Axes {X, Y, Z} + value
• Use the Move tab: select Rotation, then axes and then the value

That is four options in total.

cheers.

how do you flip a tile to point down (light brick)

Can you rotate a part less than 22.5 degrees?

Yes, change the grid size (default is medium) or disable it. See top toolbar.

Can you do that on a iPad?

No you cannot use the rotation shortcut with a touch screen. But you can can the grid size and use the gizmo to achieve the same.