Is 12 hours too long to leave a roast cooking in a crock pot/slow cooker?

I'm making a roast for lunch tomorrow and I'd like to get it started in the crock pot tonight before bed, but that will mean it will be in there cooking for 12 hours and I've never left anything in my slow cooker for that long. Will it be ok as long as I put it on the low setting or should I wait to start it?