We have stayed there 7 times and generally end up on the 3rd floor about midway back from Harbor. While you can see some out the windows, MommyWithDreams, is right you can't get the whole feel. For several years this worked great for us because a little was all we needed since my DD was afraid of the noise.
Personally for our group, fireworks are optional. My kids don't really enjoy them that much so we might watch them once in the park and any other time during our stay, catching that small glimpse out the window.
We did watch the view from the roof one time. It was a better view but there were not many chairs so we had to stand the whole time. If you don't mind missing the crowd and music it works okay. But, of course, nothing is quite like being in the park.