Motherwell have signed Middlesbrough goalkeeper Connor Ripley on loan.
Aston Villa have continued their spending spree after securing the services of Rudy Gestede from Blackburn on a five-year contract.
Having generated funds from the sale of Karl Darlow and Jamaal Lascelles to Newcastle United, Forest wasted little time in reinvesting in their squad.
A big-money approach was made to Peterborough United for top marksman Assombalonga, and the 21-year-old duly joined the ranks at the City Ground.
He has opened the season with four goals in as many Sky Bet Championship appearances and Pearce believes there is even more to come from a young talent who is yet to reach his full potential.
The Forest manager said in the Nottingham Post: "At that price tag, he was an absolute snip.
"You only have to work with the lad for a short space of time to realise what sort of character he is. He is a boy who is desperate to do well and desperate to improve.
"He came with a good scoring record and a good reputation. They spoke very highly of him at Peterborough and I know why they did now, having worked with him.
"He is an outstanding kid. I don't think he is content with where he is, with regard to the standard of football.
"He knows he can only get better and this is a fantastic club for him to get better at.
"We just hope that his form and ability keep growing and that it takes this club into the Premier League."
Goals proved to be a problem for Forest last season as their play-off push faded over the final weeks of the season, but a summer reshaping of the squad has brought in the likes of Assombalonga, Matty Fryatt and Michal Antonio and opened the floodgates.
Pearce added on the firepower at his disposal: "We do feel as though there are goals in this group, but you have to have that in this league.
"You look at Norwich who have Lewis Grabban, who has got four goals already.
"The teams who win promotion have to have goalscorers and we have to have that in our side, while also keeping clean sheets at the other end, if we can.
"But we do feel as though we have that threat."