Exactly bumpy. The fact is that rubber or tpo roofs have a finite life. Period. They will eventually deteriorate to the point that you can't coat or seal them, etc. Is aluminum perfect? No it's not. It requires you to check/maintain your calk joints twice per year. If you do that it'll stay leak free. The roof on my Layton is one piece and remains uncoated and looks great yet.
I inquired at Jayco one time about ordering a tt with an aluminum roof and was told it was not possible. Tpo/rubber roofs come with a 12yr warranty. When that's up, the roof is about shot and the cost to install a new one is more than the trailer is worth.
No thanks.