Bayern thumped Barca 3-0 at the Nou Camp to reach the final 7-0 on aggregate.
Former Real Madrid winger Robben told Sky Sports 2: "Now we're in the final. It's the third time in the last four years, but it's time to win it now!
"It's going to be a big one. Dortmund have proven over the last two, three years that they are a very good side. It's going to be a big game again which will be decided by the small details."
The Holland international added of their Nou Camp victory: "I think it's a terrific performance - a little bit of history maybe.
"You're playing against a team who have dominated Europe over the last five years and there's so much quality in their squad, and to win 4-0 at home and 3-0 away, especially this one away in their own stadium, it's amazing."