when did john rifile discovered tobacco?

I think you're asking about John Rolfe. He didn't "discover" tobacco, really. According to Wikipedia, tobacco was already quite popular at the time of Rolfe's birth in 1585, and Spain held a near-monopoly on the tobacco trade, because its New World colonies had a favorable climate for growing the most popular strains of tobacco. Rolfe was able to purchase (illegally and at what was at great risk to the person selling them) seeds from the popular strains of Trinidadian and South American tobaccos, seeing an opportunity for the English colonial settlements to muscle in on the Spanish tobacco market. The harsh-tasting native tobaccos that the Indians in the Jamestown area was not preferred by the English, and so it was not desirable for export.

Rolfe with his precious bootleg seeds set sail for Jamestown with the Third Supply Fleet (indirectly, because they were blown off course and had to divert to Bermuda and lost a lot of time and most of the fleet and supplies, which was a devastating loss because Jamestown was literally starving), arriving in 1610 to begin his tobacco work. Rolfe successfully planted and grew the bootleg seeds, and by 1612 was able to begin exporting this crop, helping the settlement to turn a profit, and later expanding its cultivation to new plantations along the James River for export. Tidewater tobacco plantation expansion promoted demand for a source of labor to clear the land and work the fields (because tobacco really depletes the soil, plantation owners were constantly looking to expand into new fields because there were no commercially available fertilizers at the time); hence the demand for slaves to grow this cash crop and increase profits.