You can rotate or flip objects (and the text inside) on slides, either by precise measurements or eye-balling it.
Tap the object that you want to rotate.
Select the rotation handle at the top of the object, and then drag in the direction that you want.
To flip an object, select Drawing Tools > Rotate > Flip Vertical or Flip Horizontal.
For more precise movement, select Drawing Tools > Rotate > More Rotation Options to see menu options.