What type of bike are you riding and how many hours a month do you
ride?
I rode bikes for years, mostly big highway tourer's. Gold Wings,
BMW's, Motto Guzzis's etc...
I do know the harder the ride the more likely you'll suffer bad side
effects.(I know many older bikers that can no longer ride cross
country because of back problems or prostate/colo-rectal issues.)
I've had 'roids all of my life and even on soft ride have had
problems. It's not just the bumps but the vibration and heat as well.
If you ride something like a Harley you'll most definitely develop
problems, especially as you get older.
It'll take preventive therapy to avoid painful symptoms.
If you do have hemorroids you'll have to take frequent sitz baths in
hot water, maintain a diet with lots of fiber and roughage and use an
ointment that contains a vaso constrictor.(I also take vitamin E and
Bio Rutin to help keep mine shrunk and soft.)
On the bike side you can get a bigger saddle, I used a touring saddle.
A King and Queen type that allowed me to move up and down on long
hauls.(I'm fairly tall and could scoot back and forth to allow me to
stretch my legs and back a bit and keep blood flow going in the back
and legs.)
If your bike has alot of engine vibration you can use isolation
bushings on the saddle mount bolts to cut that out.
You can also get a vented cushion that straps onto the saddle, kinda
like the ones made for car seats to increase airflow to the posterior.
Check out your local bike shops.