Did you ask your primary care? Or your nephrologist/transplant team?
I would think there’s a lot of variables here— for ex: how long since your transplant, any complications, or other factors that might not be obvious to most people— that are best discussed with your nephrologist or your transplant team.
Your primary care may not know enough about transplant specifics to give you an answer. If your nephrologist or transplant team isnt sure about roller coasters, in particular, maybe guide the discussion by asking if they’d have any concerns with the various forces exerted by the quick directional changes, speed factors, shearing forces, etc. That should help them to determine if there could be any contraindications.
You are smart to wonder… clearly you appreciate the miraculous gift you received, and do not want to take it for granted.
Good luck.