The Baggies landed the Benin international on transfer deadline day - parting with a club record £5.5million fee to lure him away from Sunderland.
Sessegnon has shown throughout two-and-a-half years in England that he is capable of terrorising Premier League defences, and was being linked with moves to some of Europe's top sides in the summer of 2012.
West Brom consider themselves fortunate to have secured his signature, with the 29-year-old having underlined his class with a star showing in a 3-0 victory over former employers Sunderland on Saturday.
Ridgewell said of the highly-rated playmaker: "He's a quality player and we all knew that. We saw that at Sunderland. And getting him to West Brom is obviously good for us.
"Two seasons ago he was being touted for moves here, there and everywhere, so to get that kind of quality to West Brom is great and it's a very good coup for the club.
"I'm relieved to have him in our team because he's a very lively character and every time I've played against him he's been a very good player. So I'm glad he's in our team and not the opposition."
Ridgewell has also hailed the speed at which loan signing Morgan Amalfitano has settled at The Hawthorns - with the French winger netting once and setting up two more against Sunderland.
He added: "A lot of people probably didn't know much about him but he's a tidy footballer and a very good player out on the right. He did well here and at Fulham last week.
"It's not easy to come straight in and play in the Premier League. A lot of people struggle at it but I thought he did very well and he is a very good signing for us."