sarah, rofl about the thorns!!!!
if it's still smallish in size, then it's probably a regular type rose bush (if it was a climber type, you'd know it as there'd be at least one cane that would grow outrageously long). too much sun or too little sun as well as improper soil can cause them to not grow as well as they could.
you can amend the area where you're going to transplant so that it is well-draining and has some manure or compost added. also, mulch around the bush when you've got it transplanted...just leave the area at the base of the bush clear of mulch - about an inch and a half wide. you don't want the mulch to be touching the base of the bush (or any plant, btw) as that can cause problems. also, when watering, give a good shot to the base and then do a thorough watering around the bush at the 'drip line'; let it soak in for about a 1/2 hour and then do another swing around the drip line again. the 'drip line' is the area right under the outermost leaves. watering at the drip line causes the roots to spread out to reach the soil that has the moisture and you definitely want the roots to spread out and become properly established! water every day (unless it rains) for the first 2-3 weeks. for mulch, i use licorice root mulch...it's been very good for all my plants and bushes.
good idea for afternoon shade if the sun is that bad in the pm!!
and i forgot about the tap root...tk is right! make sure you get the whole thing!!