No newbie to aikido ever does standing rolls the first time they attend a class at my dojo. That seems very unwise to me for reasons you've illustrated in this thread.
After a long time doing and teaching ukemi I think one of the most helpful pieces of advice I could give you concerning standing front rolls is to make sure your arms are extended in front of you in a circular way. Your arms should appear as though they're hugging a barrel. If your lead arm forms a sharp angle - as often happens with beginners - you'll find that you won't roll up smoothly to your shoulder, but instead you'll bang your elbow and then your shoulder as you fall forward. Extending your arm with too much of an angle to it has the same effect on your roll as a square wheel would have on the motion of a bicycle: very bumpy. Your arms should form a circle together as they extend in front of you to the ground.
(You could also try stuffing a couple of pillows into your keikogi top at the shoulders.
Hope this helps!