Is it safe to take sertraline 50 mg tablets, oxycodone/acetaminophen 10/325 mg tablets, and dexamethasone 4 mg tablets together?

Risk. Every medication has risk. Nobody can guarantee that you won't have side effect or be injured by any medication you take. If your doctor prescribes these medications for you after knowing your condition, then that means he/she feels the possible benefit outweighs the risk. You have to decide whether you agree with your doctor or not.