Household bleach isn't very strong and won't do much good, except for a couple of days maybe. Try this - it always worked for me with clogged or slow drains. Buy a small container of swimming pool chlorine powder and mix some (a strong concentration) with water. Don't inhale it - it will burn!!!!! Pour hot water in the drain and then follow with the chlorine mix, and don't flush the chlorine thru right away. Let it sit about a half hour or more, and then flush with more hot water. That will eat thru just about anything that is sitting and stagnating and giving off that foul odor. If that doesn't work (you might need a couple of applications), then I suspect that Roto Rooter is the only answer.