Welcome to the forum. Yes, tires are important and should be checked often and replaced by age, not condition.
The roof is probably the second most important thing on a RV. Check it often (or have it checked), a small leak can do a lot of damage if not repaired quickly.
You can work around the other things in the RV if they fail. If tires or your roof fail, it can cause major problems.
Now, round up the girls, get out and travel. You don't know what life will hand you tomorrow.
Don't hesitate to ask questions. That's how you learn.
Enjoy your travels.