Unless it is a mammoth sized roast you will be fine but it will likely be a bit mushy due to cooking so long. For a large roast 5-8 hours is usually about right. I think I used to have a chart for venison cook times to reach full pasteurization but I can't find it at the moment.
If you follow this link it has a ton of great info regarding times/temps/thickness of other meats though.
douglasbaldwin.com/sous-vide.html
Table 5.1 shows the time for beef which would probably be closest.