Lewis-Roberts tested positive in a random test after playing for Toulon in last season's Pro14 final against Toulouse.
Steffon Armitage failed a test following the same game. Armitage was cleared in November after the club successfully argued he had taken morphine for medicinal purposes. Lewis-Roberts rejoined Sale after that Paris final and the Aviva Premiership club announced that the 32-year-old had been found not guilty.
David Barnes, rugby director for the Rugby Players' Association, said: "This was the correct decision and we are relieved that an innocent player has not had his reputation unnecessarily damaged.
"For Eifion to have had this hanging over him since the test took place in June 2012 is unacceptable in professional sport.
"In this case, as the panel have agreed, there was no intention on the player's part to enhance his sporting performance and he has fully co-operated with the investigation to prove his innocence."
Lewis-Roberts, nicknamed Fridge, revealed on Twitter he is undergoing a shoulder operation on Wednesday.
He posted: "delighted to have cleared my name! shoulder op tomorrow onwards and upwards ready for a great season next season!"
- Sports & Recreation
- Steffon Armitage
- Aviva Premiership