Small Engine Troubleshooting Problems? Ask a Mechanic Now.
If the mower has Caught fire, I personally and Professionally, would say it does not need to be in operation. It is a danger to you. I would personally find a Toro Dealer locally, and take it to them.
I am a local Toro Dealer here in TN, and if you hit a root, most likely it has damaged the Crankshaft. Once the crankshaft is damaged, it usually is not worth repair after this. The crankshaft is bent, and has caused the oil to lean out the bottom on the engine. Without replacing the crankshaft and the oil seal, among other internal parts most likely, this mower will never be 100% operational and safe to be used. I am a BIG safety person when it comes to my shop, and if I have a customer bring in a mower with a bent crankshaft, it will not leave my shop with a blade on it. It is not safe, and they should not have give it back to you this way. I would complain to the TOP of HOME DEPOT Management
If you give me the numbers off of the tab above the muffler, I will look up the parts you would need at a minimum, but I am 100% sure, this mower is DEAD and not worth repairing due to cost of repairs vs the cost of new mower. I sold this mower for about $350-$375 if I remember correctly, and you would be looking at close to that if not a little over in repairing