Hi, Jutta! Thank you so much for coming to visit us with your question.
You will find throughout
Walt Disney World that virtually every queue will be wide enough for you to take your rollator with you. It will work similarly to having a wheelchair, in that when you get to the point in the line where you are boarding a ride vehicle, the cast member can take the rollator for you and have it there for you when you are finished on the attraction.
If yours has a built-in seat, the ability to have it with you in the queue can really be a bonus. I know many guests, including my own parents, sometimes needed to sit and rest a minute if a line was particularly long.
They don't rent rollators at Walt Disney World, however, you can rent
Electronic Convenience Vehicles (scooters) and
wheelchairs. These are available near the entrances at all of the theme parks. You may want to do a Google search for medical equipment rental in the Orlando area. Some of them are able to rent things like rollators, however availability and delivery of those items may vary.
Walt Disney World is very accommodating to guests traveling with disabilities. Don't be afraid to ask a cast member or at guest services for available
disability services at Walt Disney World.
Have a magical visit!
Anna