From BlenderWiki

Rotate

Description

Pressing R will enter the “rotate” transformation mode where the selected object or data is rotated according to the mouse pointer’s location. This mode uses the angle from the pivot point to the mouse pointer as the angle for rotation, so moving the mouse further away from the object/data will give more fine-grained precision (i.e. the mouse movement will affect the rotation less, for the same mouse distance moved).

Rotation in 3D space occurs around an axis, and there are several ways to define this axis. But in general an axis is defined by a direction line and a point that the line passes through. By default the axis is orthogonal to your screen (i.e. it is going into or out of your screen). If you are viewing the scene from the front, side, or top 3D view windows, the rotation axis will be parallel to one of the global coordinate system axes. If you are viewing the scene from an angle, the rotation axis is angled too, which can easily lead to a very odd rotation of your object. In this case, you may want to keep the rotation axis parallel to the coordinate system axes.

Rotation in header.

As you rotate the object the angle of rotation is displayed in the 3D window header (Rotation in header).

Options

LMB or ↵ Enter

Confirm the rotation, and leave the object or data at its current rotation on the screen.

MMB or selecting Scale on Axis option

Constrain the rotation about the X, Y or Z axis, see Axis Locking.

RMB or Esc

Cancel the rotation, and return the object or data to its original rotation.

Wheel

Object mode

Zoom in/out

Edit mode

• Proportional Editing disabled: Wheel does zoom in/out
• Proportional editing enabled: only vertices within the circle of influence are moved. In this case scroll the Wheel to change the radius of the the circle of influence.

R (Trackball)

Pressing R while already rotating toggles the rotation mode between a single axis rotation (either aligned to the screen or around a certain axis) and a two axis, “trackball” rotation. In “Trackball” mode, the rotation of the object is controlled by both the X and Y location of the mouse pointer, similar to the trackball view rotation mode. This can be a quick way to rotate an object into place, without having to keep changing the view rotation while adjusting. However, it is more difficult to use than the simple rotation.

Point of rotation (Pivot point)

To select the point of rotation that the rotation axis will pass through (so-called Pivot point)), use the “rotation/scaling” button accessed in the header of the 3D window, . For a full description of the different pivot points, see their dedicated page.