Roslagsleden can be done a loaded bike, but I'd def prefer to go somewhere else, it's bumpy, technical, overgrown, not that much fun tbh.
I've done most of the Swedish safari route, liked it alot. I'd go on a hardtail. Sörmland is lovely.
Gotland is great, I'm working on a route along the coastline, will be around 450 km, excluding Fårö. Mostly gravel thou.