I did try that a few years back, because I'd had some at a bar that was done that way and it was delicious. Mine came out tasty but tough, but I think it would be worth some more experimenting. I don't remember how long I roasted it, but I do remember that I looked up roasting time for brisket (not corned) in Joy of Cooking and followed that.
Have never tried slow roastiing corned beef, but thinking it might take even longer than in a crock pot or on stove top? Would try it if I had a cooking source where I could just get it started and walk away... for SEVERAL hours, I'm thinking!
Reluctantly admit to trying to cook corned beef in MICROWAVE one time!?! WHAT was I thinking?? I guess technically it was done in about 10 minutes, but HARD as a bowling ball... ended up finishing it (to fork tender) iin big pot the way I should have from beginning.
Have cooked a CB till almost there, then transferred to stove top smoker with a pastrami-ish rub... made great sandwiches.
Not corned beef but another SLOW cooked thing... ribs. Last summer, took 2 nice racks of baby backs along on a road trip froom NJ to WV... with recipe from Good Eats... something like "whose your baby back". Had a fairly spicy rub... salt, brown sugar, and messa spices... rubbed on and wrapped in a few layers of foil to sit over-night. Then into oven, with a liquid mix added for 2-3 hours at a pretty ow temp... maybe 275-300. Last step was a quick sizzle on grill... maybe half an hour... marinate from foil pouch cooked down till a "glaze". They were GREAT.