I burned a granite roaster by letting the liquid
boil away and it became crusty and a mess. I've
tried soapy water soak, vinegar for overnight and not much has helped. Have I ruined it and just need to throw it away? Is there anything else I can try? Thanks for any suggestions.

Wait for suggestions from others but as a last ditch effort, you could try oven cleaner.

Sudsy Ammonia is what I found works the best and easiest. Completely fill the pan (up to and just over the burnt crust) with straight sudsy ammonia. Place the lid on or have it in a plastic trash bag to seal in the fumes. The garage or outdoors over night will be the best place. By morning everything should be easy to clean off.

This works really well on broiler pans and grill grates too.

I agree with Conrad, Sudsy Ammonia in a small dish left in the oven over night will clean it up all you will have to do is wipe it out.

Sounds like a good idea BUT, if it doesn't work, my first thought was Easy-Off Oven Cleaner.

Fill the pan with water and boil again on the stove top. The reheating should loosen everything so it scrubs right off.

I have also used oven cleaner on those large roasting pans too. Plus use the steel wool pads to scrub the pans.

Good Luck and let us know what works!

Not trying to sound 'flippant', but I would prob turn it into a flower pot or put in garage to hold potting soil etc.

I once threw out a cast iron pot when I burned beans in it...I was young/dumb and didn't know it was sup to be seasoned first.

Once cooked a Calphalon non-stick pan dry!?! Food was stuck iin bottom and didn't want to even try to dislodge it. Somebody (here maybe) suggested... fill as full as possible with water and bring to boil... a little slow so it didn't just boil over. Then several LIBERAL spoonfuls of baking soda... which proceeded to bubble up and a bit over. After it sat till cool enough to handle, hadda ladle out enough water so I could make that u-turn to dump in the sink. ALL of the crusty stuff came right off... maybe becasue when I burned the food it was on low??

WOuldn't hesitate to try oven cleaner on roaster if all else failed. Kinda inherited an OLD one after husband's grandfather passed away. It was so crusty on the outside that you couldn't even SEE the "speckles". Oven cleaner did the trick.

As for burned on food in cast iron... CI is pretty near indestructible. When I find another piece to add to my collection, out comes oven cleaner... in HOT weather. If it's cold, I'll fire up self-clean cycle in oven and end up with only ash (and maybe a little rust) to deal with... then a good round of reseasoning.

My suggestion would be to put cream of tarter in the pan and just a small amount of water (1/2 inch or so) boil till the crusty stuff is dislodged.

Dishwasher detergent. The powder, not the blocks. Cover the bottom of the roaster about 1/4 inch deep. Put the roaster where it will be undisturbed for at least 8 hours. Then fill it with very hot water to cover all the burned-on ick. Leave it that way for at least 8 hours. Most of the mess will disolve, the rest will get so soft you can remove it with a dish brush or net scrubby.

If you get the dishwasher detergent-water mixture on your skin or clothing rinse it off as soon as possible. Its as harsh on your skin as it is on the burned-on food.

I bet most of these suggestions will probably work well to clean the pan. Waiting, soaking, heating should all be helpful too.
Please post back what you tried and how well it worked for you?

I am notorious for burning pans over my lifetime. I use either the amonia or boiling/baking soda methods. Sometimes have to repeat but both do work.
The amonia in the garbage bag works really, really well for burner pans that are stubborn too...when I also boil something over!

I've tried the boiling water and left it till it cooled. No result. I have the pan with ammonia and Dawn dish soap soaking and in a large plastic bag. Will see what tomorrow brings. I'd forgotten about the dishwasher powder. The baking soda and/or cream of tartar are worth trying too. Will let you know what finally works. Thanks for all the suggestions.

I did the ammonia trick with Dawn added. It did a pretty good job. I was able to scrub a lot of the gook out of it. My daughter also suggested using an unused dryer sheet (softener) in the pan in very hot water. She said I could just scoop it out the next day. I'm trying that now just to see if it gets the last little bit. Will let you know.

Thanks to all the ladies with comments. I'd say the ammonia did the best job. I will use that again if I have the same problem. The dryer sheet in hot water did nothing as well as boiling water in the pan and letting it cool. I feel I can use the pan again and will watch carefully how much liquid there is in it.