The young Magpies meet the Hammers at Whitley Park on Saturday (kick-off 12pm BST), aiming to bounce back from a heavy away defeat against Reading on Monday - with Neil Redfearn's side losing 6-0 to the Royals in their opening Premier League 2 fixture of the season.
And Longelo, 19, who joined Newcastle from the Hammers last year, is hopeful United's second-string can get off to a winning start against his former club, who were relegated from Premier League 2 division one last term.
The left winger told nufc.co.uk: "It is a very important game because the first one didn't go quite as planned. We didn't come away with the three points so the next game, we are targeting a victory.
"We've actually learnt quite a lot from the game. We watched the clips back and the coaches have told us what we have done wrong. There were certain things that we did correctly but we need to make sure that we put it right against West Ham tomorrow and we come away with the three points.
"They like to keep the ball in their midfield third but they aren't scared to go out and attack. They play exciting football but I think we can definitely match them and come away with a positive result.
"Last season, we were very close to going up. It just shows the quality we have in our team and I definitely think we can match our opponents. I don't think we are a team that are to be taken lightly."
Longelo also faces the prospect of going toe-to-toe with younger brother Emmanuel, with the 18-year-old currently playing for West Ham's under-23 squad.
The Hammers got their Premier League 2 campaign off to a winning start following a 3-0 win against Fulham but Rosaire was full of fighting talk ahead of Saturday's clash, remaining fully focused on the task ahead.
Longelo added: "Just before pre-season started, I was speaking to my family about it. Everyone is very excited and they are all coming up to watch the game. I've always wanted to play against West Ham ever since I left them. I'm looking forward to the occasion.
"I'm also looking forward to possibly going up against my brother. He plays on the left flank like myself and I told him once the referee blows the whistle, I don't know who he is. I'm just focused on the game ahead and once the referee blows that full-time whistle, I will remember him again!
"It's very important to get a good start because, last season, we had a slow start but we managed to pull it back. This season, we would prefer to start faster and keep it going that way so, come the end of the season, it can be easier for us.
"Everyone is looking forward to the games coming up as we like tough games. It gives us a test and to showcase our ability so I don't think we're going to be backing down from it and are fully focused and ready to go.
"I like the challenges from the bigger games as it gives you a chance to test yourself against the better players."
Tickets for the game at Whitley Park are available at the turnstiles, priced at £3 for adults and £1 for concessions. Admission is free for season ticket holders and members.
