Williamson said: "I don't believe it, I'm going to f*****g cry. Sorry, I'm crying.
"This team has been together for a really long time and we've been working really, really hard to get to the next level.
"And to do it on the biggest stage, and I think some people just had the game of their lives and that's what you need, and we did it. I'm just so happy."
Russo added: "It feels surreal. We knew we could [win]. We believed since the moment our Champions League journey started.
"We knew that we had the capabilities, we knew that we could be good enough. It was just about going and doing it, and we've done it."