How to rotate a part/device in Eagle (schematic view) using keyboard-hotkeys only?
It is possible to acheive the behaviour you wish.
Eagle uses a command based system, and mouse clicks are no different from other commands - they have text based equivalents.

Left Click: (@)
Right Click: (&gt;@)

You can add additional modifiers for things like shift (s), ctrl (c) and alt (a). So for example, shift+right click would be (&gt;s@).
Coordinates can also be entered using this syntax, replacing @ (current mouse position), with a value such as (&gt;s 1 2) - shift right click at coordinate x=1/y=2 in the current grid units.

Putting this together, you can assign a keyboard shortcut (Options-&gt;Assign) for whichever key combination you want, and set the action to perform rotation in one of three ways:

If you want to rotate whichever part you are currently hovering over with the mouse (i.e. have not clicked on yet), you can use the command rotate (@). This will activate the rotate command and immediately click and rotate whichever component or object is at the current cursor location.

If you want to rotate an object you are currently moving - i.e. you've clicked on it with the move command and its currently following the mouse around - you can use the command (&gt;@) which will perform a right click at the mouse location. For the move command this right click performs a rotation of the selected object without letting go of it.

If you want to rotate the current group, you can do the command rotate (&gt;C@) which will CTRL+Right Click with the rotate command, which will rotate the current group.