I suppose you could use a protractor model, but the ones in the 3D warehouse do not appear ideal for the purpose. Unfortunately the dimension lines do not (to the best of my knowledge) reveal angles.
However, as the room tool (and the wall tool) do show angles and distances while drawing.

So finding angles in the horizontal plane is easy: Click with Room tool at starting point and move cursor in desired direction, use ALT to toggle magnetism on/off. The tool-tip will show angle/distance between starting point and cursor. Press ESC to finish without actually drawing a room.

Finding angles in the vertical plane is trickier. If you have one object (a wall) you can select, export, import, rotate and measure the angles as described above. But usually it is easier just to use a spreadsheet, calculator or other calculation aid (e.g. Geogebra) to calculate the angles.

The Thread: Splitting sloping walls? discusses some questions related to angles in the vertical plane.

ok