。
You've come up in the world since I last saw you.
Literal
I [subject-が] last [in-に] you [to-に] met since you [topic-は] rose-[confirmation-ね].
以来 ('since, from [that time] on') takes the past clause as the start of the duration. 出世する ('to succeed in one's career, to rise in the world') is a classic phrase about upward mobility — literally 'to come out in the world.' A slightly envious or admiring compliment between old acquaintances.