Since you're reminding them daily who Roo is, that should help a lot.
As for hens being gang raped, don't worry about that. They can't get raped. Roosters don't have penises and if a hen really does not want to mate, she quite simply will not move her tail feathers out of the way.
Despite the complaints, they put up with a lot of rough treatment and still choose to mate; a rooster will mate just the same if a hen is inclined to mount him, complaints and all, squatting and moving his tail feathers out of the way. It really doesn't matter who's on top, if the animal underneath understands mating is being attempted and acquiesces, it will cooperate and successful mating occurs. I had a hen who liked to be on top.
Females have internal mechanisms which sort sperm and even destroy unfit sperm, so if a hen mates with multiple roosters only the most genetically dissimilar and healthy rooster's sperm will get a chance. There's been a lot of interesting research and studies coming out about this lately, confirming a lot of things I had suspected from observing how my breeding experiments have worked out.
If your roosters are mistreating your hens and causing damage, they're not good roosters, because a good rooster won't harm a hen and is very careful while mating. Getting more hens might help but quite often a rooster who is rough and removes feathers, pecks, scratches, spurs, etc a hen, and pushes for mating when she responds negatively, is going to continue to pick on his favorite even if you give him 100 hens.
It's a mentality which is heritable, and it's not caused by nor alleviated by the ratio of hens to roosters.
In this area it comes down to what you're willing to tolerate from your males. I only allow respectful behavior, so if any of my hens rejects a rooster's advance, he will back off instantly. This means no hen has a rooster jumping on her when she's not ready to mate because she's injured, or ill, or brooding, or whatever her reason for being unwilling is. It's not natural for a male to disregard the female's wellbeing, as this cripples or destroys his chances of passing on his genes. Taking every care of the female is the natural instinct but we've bred that out of many of them through unnatural keeping practices sustained for generations.
From my limited experience with Guineas, they are terrible bullies, and I had to get rid of mine while they were still chicks because they were trying to disembowel turkey chicks the same size as them. I think your best bet is to get a few more hens so separate flocks can be established. Possibly getting rid of any nasty roosters is another option, but building another cage will help, and possibly putting up more perches can help too. I put perches at a few inches off the ground and every few inches above that at the corners of the cages, so babies can learn to perch, sick or hurt birds can still perch, bullied birds can duck under and behind the perches to escape bullies, and less able birds can climb onto the higher perches bit by bit. Obstacle courses discourage bullies. I cull bullies but breaking the pattern of behavior can help for those who are more tolerant than myself.
Your solution may be nothing like what I've recommended/suggested but I hope you find it soon. Should mention, I guess... Short term solution for preventing bullying is shackling. Get a soft thick shoelace of rope and tie around each ankle of the bully bird's feet; not so loose it goes over either foot or knee; no weak knots that can slip or tighten; leave enough length between the feet so the bird can walk normally, but not run. This way the bully can dust bathe, walk, scratch, jump up on perches, etc normally but can't run after another bird to bully it. I wouldn't do this around guinea fowl lest they kill the shackled bird, but it might work on them too. I've used that on hyperaggressive turkeys bent on killing other birds. They charge after their intended victim only to fall on their faces. Discourages them so much they stop automatically lunging at their victim. But of course tying up a bird's ankles comes with risks of getting caught in things, and if you've tied bad knots they might tighten and cut off circulation, so if you try this method, be careful.
All the best.