With selector tool, if you hold shift while moving a rotation handle : then rotation comes from the opposite handle (if this sounds clear...). Might be useful, depending on the shape of the path.
The best way remains to drag the rotation center, as Polygon explains. Use snapping options (Nodes>Cusp Nodes and Other Points > Objects rotation centers). Once done, you can reset rotation center by shift-clicking on it (Thanks to Tyler for this useful tip).
Beginners' Questions Rotating a Line
Inkscape.org
Is there a way to rotate a curved line with one end of the line being an anchor rather than rotating around the center point?
In "Rotation" mode you can drag the "anchor" where you want it to be.
With selector tool, if you hold shift while moving a rotation handle : then rotation comes from the opposite handle (if this sounds clear...). Might be useful, depending on the shape of the path.
The best way remains to drag the rotation center, as Polygon explains. Use snapping options (Nodes>Cusp Nodes and Other Points > Objects rotation centers). Once done, you can reset rotation center by shift-clicking on it (Thanks to Tyler for this useful tip).