I would probably start with SID the seams around the roses (or the serpentine stitch could be used over the seam lines). Going all the way across the quilt top for each seam (think north to south), then turning the quilt and Sid the east to west direction. Making a square around each rose. This would stabilize the sandwich. Then I would come back and outline the roses and stitch a spiral within them as Tartan suggested. As to the pieced border a continuous "x" stitched from corner to corner of each square would be nice. To finish it up how about a piano key border from the pieced border out to the quilt edge? Just some ideas - I'm sure whatever you decide will be perfect as this it such a beautiful top.