Make a big hole. About twice the size of the pot. Fill half full with dehydrated manure. This is your one and only chance to get fertilizer UNDER it.

Remove from pot. Open the root ball a bit. Place in the hole. Find the "knob" at the base. Roses are all grafted, onto the roots of wild roses. You want the 'knob' to sit just on the soil line. So set the root ball accordingly and start filling in the hole. Gently lift if it settles too low as you are filling.

Over time, once in a while a shoot will poke through the ground from the wild rose roots. It is from below the knob. These you want to cut immediately as they will take hold and kill off the heirloom, or whatever rose is grafted on. You will cut it BELOW the dirt line, so it can't get any sun and grow more.

Plant them well apart, I think it is like 2 or 3 feet. Maybe there are some instructions that came with them?

Top with mulch if you want, but make sure you don't smother that 'knob' with the mulch. You want all new shoots off that knob and above it.

Good luck!