Rotate the input by PI/6 radians clockwise:

rotate=PI/6

Rotate the input by PI/6 radians counter-clockwise:

rotate=-PI/6

Rotate the input by 45 degrees clockwise:

rotate=45*PI/180

Apply a constant rotation with period T, starting from an angle of PI/3:

rotate=PI/3+2*PI*t/T

Make the input video rotation oscillating with a period of T seconds and an amplitude of A radians:

rotate=A*sin(2*PI/T*t)

Rotate the video, output size is chosen so that the whole rotating input video is always completely contained in the output:

rotate='2*PI*t:ow=hypot(iw,ih):oh=ow'

Rotate the video, reduce the output size so that no background is ever shown:

rotate=2*PI*t:ow='min(iw,ih)/sqrt(2)':oh=ow:c=none