Roll rotates active structures continuously around the specified axis, defined relative to the viewer:
Not implemented: the use of roll to manipulate active bond rotations.
If angle is specified, the structure is rolled through that angle (given in degrees) for each frame. If angle has a negative value the direction of the rotation is reversed. Frames, if specified, indicates the number of image update frames over which the roll operation is carried out. If frames is not specified, the structure continues to roll until explicitly turned off with freeze. Note that two or three rolls may be active at the same time; that is, the user can roll the structure around two or three axes simultaneously.
roll x 2 90rolls the model 180 degrees over 90 image updates (i.e. 2 degrees on each frame update). Commands continue to be processed while the requested motion is in progress. To pause command processing until the motion is finished, use the wait command. To halt an ongoing roll, use freeze.
See also: rock, turn, select, cofr, set independent, movie-related commands