This patch is a first implementation to make the Vector Rotate node work with Geometry Nodes.
{F9794869}
This node allows for easy rotation of direction based attribute falloffs like linear or radial gradients either directly with the node or controlled with an empty.
Linear Attribute gradient (visualized with Eevee) rotated by an empty:
{F9794879}
Here's the scene I used in the recording:
{F9794880}
**Further Considerations**
It might be better to expose the input values of the Vector Input because I found that you usually need to add a Vector input node anyway to work with this node in Geometry nodes.