I would say Roll Ups because they have less chemicals.
Follow the site below to find a table of toxic chemicals in Cigarettes.
Notice it includes Carbon Monoxide, Formaldehyde, Ammonia, and Arsenic.
The home page to the linked site has a passage that states, "While these ingredients are approved as additives for foods, they were not tested by burning them, and it is the burning of many of these substances which changes their properties, often for the worse. Over 4000 chemical compounds are created by burning a cigarette, many of which are toxic and/or carcinogenic."
If you are inhaling these chemicals, then ones around you are inhaling them. Rolling tobacco may have more tar, but you would be making the people around you a bit safer, and you yourself would be inhaling less toxins.
I guess what you have to ask yourself is, Do you want Tar or Chemicals?