"It is happening very quickly for him at the moment and the important thing is that he keeps his feet on the ground - which I am sure he will do," says Glenn.
"It is part of my job to make sure I keep talking to him in the right manner which I do on a regular basis, almost daily, to make sure he stays calm and assured.
"But that is fairly easy for him because that is his nature as a human being.
"He has got the most wonderful personality and a terrific mentality to be a top class footballer."
Glen made his Hammers debut as a substitute in the 4-2 defeat at Charlton Athletic in January, just days after sitting on the bench in the 3-1 loss at Arsenal.
He then came on at Old Trafford in the 6-0 FA Cup defeat to Manchester United, before his full, and indeed home, debut against Blackburn, which coincided with the first Upton Park league victory of the season.
He has, to use the cliche, not looked back since then, playing every minute of seven consecutive games and picking up a couple of bookings with West Ham winning four, drawing one, and losing two of those matches.
But for Roeder, it is important that Glen does not rest on his laurels and he says: "What he has shown us already has set a benchmark for himself which he has now got to push up higher and higher over the coming seasons.
"Who knows where he will end up, because for me he has got everything you look for in a modern-day full back other than experience at the moment - which he will get playing games.
"He works hard on all parts of his game - his touch, his passing - and I am sure, though it is happening so fast, we will just be able to check it back if we think it is running out of control.
"But I don't think it will. I am sure he will handle it and keep his feet firmly on the ground - which he must do.
"If he does that, it will allow him to improve quicker because he will be able to retain a sense of reality about everything."
Fans unable to make the trip to Southampton on Saturday may like to see if they can spot the next Glen Johnson by watching Kevin Keen's under-17 side in their FA Premier Academy play-off clash against Everton at Little Heath. Kick-off is at 11am.
The match after that, incidentally, is at Boddymoor Heath against Aston Villa on Saturday, April 26, at 12pm.