can i ask 1 question why do you want to roast it? 
best bet is making a nice stew with the rabbit. 
1 large cooking pot with lid 
take 1 rabbit cleaned an jointed  
peel and slice 2-4 carrots depends if you like lots off veg or making for a few peeps 
peel an dice 4 spuds or how many you think you will need when cooking for 2 i use 4 largish spuds 
peel an roughly chop 1 large onion 
place all in the large pan with the jointed rabbit an cover with water an place on  a medium heat till it boils then let it simmer for 2-3 hours if you in no rush, 
or if you have a slow cooker place all off it in