Depends on the rooster's personality whether he'd be okay with the youngsters. Some of them have strong paternal instincts and will adopt and take charge of chicklets and even fairly young chicks, although I've never had one willing to brood chicks and keep them warm. (I did have a guinea fowl rooster who'd brood chicks or keets, rather, but guineas are different in many ways.)
The old dude rooster, Henry, who's in with my brown-egg-layers now, I let him start interacting with the little wanna-be layers back when they were about six weeks old and well enough feathered not to need heat anymore and be out in their eventual permanent pen. He took an interest in them right away, first through the run wire and then when they first began timidly foraging just outside their run, and would tidbit for them if I provided a tasty bowl of krums or something else. It eventually expanded to him calling them when he found something good to eat in the yard, a bug or some grass or whatever, at which point they were following him and he became a reliable guardian and I started letting him live with his new little flock full time. He was also very good about not trying to mate with them--a well-socialized rooster shouldn't be trying to mate with anything that's still got a peeping chick voice, which is what a 'chicklet' is to me--until they were mature enough, but then he WAS already 6 at the time, so maybe not as driven to breed as some. As for the other adult roosters I had on hand when I first got those chicks...no way! All they saw was jailbait, no paternal instincts at all to inhibit THEIR drives. Like I wrote, you need to know the rooster and some WOULD work out as temporary chicklet dads until the pullets became mature enough to become his harem. But most roosters...not a good idea to put them and very young pullets together...the pullets would suffer and might well be injured. Luckily, you can tell pretty easily and quickly who the good 'dad' roosters are and who aren't, just by how they respond to any new chicklets at first meeting. It's evidence of the care-taking and protective instincts you'd be looking for and want to see come out...not the breeding instincts!
I should mention that this particular rooster who worked out for me given a similar situation to your own was raised by a broody hen and grew up as part of a big mixed flock from day one, which really aids in developing normal, well-socialized adults, whether roosters or hens. But instincts are pretty tenacious when it comes to chickens. Every one of them deserves to be given a try.
Good luck with your own guy and hope things work out one way or another...