Final answer:
John Rolfe played a pivotal role in Jamestown's success by cultivating a profitable tobacco crop, which became Virginia's staple economy.
Step-by-step explanation:
The best description of John Rolfe's role in the Jamestown colony is that Rolfe was instrumental in building the tobacco trade in Virginia. He did so by introducing a new variety of tobacco known as Orinoco, which was smoother and sweeter than the native strains. By 1612, he began planting this tobacco in the Jamestown colony, which not only improved relations through trade but also became the highly profitable staple crop that the Virginia Company had been seeking. His success with tobacco cultivation led to the establishment of plantations and contributed significantly to the economic sustainability of the colony.