There are several spoke-like patterns on the rosettes folio.
They could be domes, tents, water wheels (like a mill wheel), fountain cisterns, or any number of things.
A couple of them remind me of mill wheels, like this early medieval drawing (note the way the pipe and the water are drawn):
Wikipedia
British Library, The Lutrell Psalter
There are also water-lifting wheels for wells and for irrigation (also to move water out of mining sites).
For comparison to the western drawing, here is a Persian wheel:
Here's a further idea for the spoke wheels... some kind of crank mechanism... there were many different kinds of wheel-cranks in the Middle Ages and some were quite large (note that there are Ghibelline merlons):