According to the US Centers for Disease Control, in 2016, there were 63,632 drug overdose deaths in the United States. The CDC further estimates that of those, 42,249 deaths involved any opioid.
The CDC reports that in 2016, 15,469 deaths involved heroin; 14,487 deaths involved natural and semi-synthetic opioids; 3,373 deaths involved methadone; and 19,413 deaths involved synthetic opioids other than methadone, a category which includes fentanyl. The sum of those numbers is greater than the total opioid involved deaths because, as noted by the CDC, "Deaths involving more than one opioid category (e.g., a death involving both methadone and a natural or semisynthetic opioid such as oxycodone) are counted in both categories."
Hedegaard H, Warner M, Miniño AM. Drug overdose deaths in the United States, 1999–2016. NCHS Data Brief, no 294. Hyattsville, MD: National Center for Health Statistics. 2017.