I did a little bit of research on this and it seems the distinction is successful colony. Roanoke, NC was more an exploratory expedition that didn't take hold whereas Jamestown was colonized for the purpose of settlement.
"Meanwhile, Grenville was delayed in leaving England for the supply of the Roanoke colony. This placed the colonists in a desperate predicament. This fact, the troubled state of Europe and America, making war with Spain now practically inevitable, and the unaccountable delay in the arrival of Grenville's supply fleet caused Lane to ask for passage to England. When Drake sailed, on June 18, 1586 he carried the colonists home with him."
State Library NC
"They sailed up stream for fifty miles, and, on the 13th of May, 1607, began the settlement of Jamestown, which was the first English Colony successfully planted in America."
Colonial Ancestors
Granted, it's a minor distinction but one that any proud Virginian would want to assert. IMHO.