Don't sweat the force. The rolls themselves will survive more force than you're capable of putting out, the gears as well.
There are some issues with older mills being marginal in terms of strength on the gears that mesh the two rolls together, if the rolls are far apart, but modern mills aren't as fragile. (The issue is that gears are designed to mesh at one, known, diameter. The meshing gears on a RM are on the ends of the rolls, which can move, which means that those gears have weird teeth, and they can mesh at any random diameter, which means that they're weak when only meshing at the very tips, as they would do when the rolls are fully open. Modern rolls have a couple of ways to get around this, so it's not such an issue.)
The other issue is pounds per square inch. The rolls themselves are usually what's called 'case hardened'. Which means you've got a thin skin of hard steel over a softer core. Works well for a variety of reasons, except, it's vulnerable to cracking if you get a point load that's strong enough to crush through to the softer core. Then the skin cracks, sort of like the chocolate shell on a cake roll. That's the origin of the 'don't roll wire' rules. You can roll wire, especially once it's flattened a bit, if you take light bites, but the idea is to keep the PSI down if you can. So wider sheet is better, etc. (and if you're going to roll flatten wire, do it at the very edge of the roll. That way if there's a problem, it's at the edge, where (A) the roll's stronger, and (B) it's on the edge, and can be avoided.))
Any decent mill should be able to take everything you can put out, and more. Don't tighten the rolls to the point where you can't crank the handle, but you're good anywhere up to there, at least with the mill you've got. One of the cheapo imports from god-knows-where? Baby those. I got one cheap once because the handle had snapped in half, under the brutal treatment of a woman who might have weighed 100 pounds dripping wet.
The only time I can think of where you want to push hard is roll printing, since you've only got one shot. Otherwise, take a couple of lighter passes, it'll be easier cranking. Metallurgically speaking, you should take heavier passes, but we're not normally pushing the metal nearly as hard as we could (or should) so it's not such an issue. (Short form: Yes, light bites are suboptimal, but so's the whole procedure, so it doesn't end up being any worse, and it's easier work.)