Frozen pizza kept at room temp (23 C) for 48 hours - safe to use?
Any perishable food (in this case I would be concerned about the ham more than anything) left at room temperature for more than 2 hours should be considered unsafe, even after cooking. Considering we're talking about a frozen pizza and not a full beef fillet, why take the risk? If it's been in the fridge, however, you may be ok.