That's hard. You'll probably have a good chance of doing this successfully if the person has fallen deep into his/her sleep, or much better, if that person has trouble waking up. Roll your hand across them (like kneading dough) in the direction you want them to move and, with any luck, they will assist and follow your lead (preferable to a sharp elbow in the side).
Read what visitors of Experienceproject.com suggested on "how can you make someone roll over in bed without waking them up?". See their answers (that might give you more ideas) here.
In an article published at ABC.net.au titled as Why do we roll over when we're asleep?, it says: Rolling over in bed is something we take for granted, yet it appears we know very little about this basic human movement.
Dr Harriet Hisc0ck, a pediatric sleep specialist at the Royal Children's Hospital Melbourne thinks that rolling over during sleep for adults and children is simply a matter of getting comfortable, which was agreed by Dr Peter Roessler, a fellow of the Australian and New Zealand College of Anaesthetists.
Roessler thinks that movement while we are asleep is a protective mechanism to prevent problems developing from prolonged pressure — such as reduced blood flow to certain parts of the skin.
Sufficient sleep might offer a big boost for your health, mood, sex life and weight. Read WebMD's 9 Surprising Reasons to Get More Sleep.
Discover the secret to getting good sleep every night at Helpguide.org.