Ry'ac does have a symbiote. Teal'c gave him his in the first season episode "Bloodlines". And we don't know if he started using tretonin, even by the time of Season 8's "Sacrifices". We know that many of the female Jaffa gave up their symbiotes to go on tretonin, but we never heard whether Ry'ac did as well (he had not given up his symbiote by the time of Season 7, "Orpheus").