Rollo would hold the title of Duke of Normandy and by 1020 his descendants, the ‘Normans’ would continue to conqueror lands west of the duchy that included the island of Mont Saint Michel.
The existence of Gisele is disputed, and this story is probably a myth, there was a lot of forced 'bending of the knee' in those days
You can read more about this period in time in my blog on my website at
meanderingthroughtime.weebly.com/tosny-of-normandy.html