You could use a batting... but I would not.. depending on the fleece it could be quite thick . I would take the fleece and roll it up as if you were to roll for quilting and see if you can handle the over all volume that will have to fit into your machine.
The fleece will be quite warm so the batting really is not required.
Consider tying or machine tacking as an alternative to quilting if you find the quilt roll will be more than you want to handle.