Firstly, do NOT accept liability for the accident, that's what you pay your insurance company to do.
Secondly, IMO, it depends on how many exits the roundabout has. For instance, there's one not far from me that has 5 exits and is a 2 lane roundabout. I stay in the left lane for exits 1 - 3, the right lane for 4 and 5, which make it different from other, smaller, roundabouts nearby where I'd be in the left lane for 1st exit and right lane for 2nd and 3rd exit.
Does that make sense? Seriously, leave it to your insurers to sort out.
The main thing is nobody got hurt, accidents happen and it's only chunks of metal at the end of the day ;o)