Well that's not an easy or recommended way because it's kind of difficult AND it depends on what kind of rose your friend has. If it's a floribunda, hybrid tea, or grandiflora it's probably a grafted rose and these cannot be grown successfully from a transplant because they need to be grafted on a wild root stalk. If it's an older rose you can try taking cuttings about 6 inches long, strip off the lower leaves, dip in rooting power (available at garden centers), and then plunge the cutting into a sterile medium such as perlite or vermiculite. Keep them in a bright spot, but out of direct sun and tent them with some plastic wrap to maintain soil moisture till they root. Then, you can move them to individual pots and grow them till large enough for the garden. OR, you can find out what kind of rose your friend has and just buy a new one that will bloom the first year for you without the hassle."