Brett A

I pretty strongly disagree with this; if you're careful with your initial purchase, there would never be need to change your setup. You may want to, but you'll never need to. This stuff is expensive, I doubt most of us would choose to spend more money than we need to. (That's money we could spend on campsites and peanut butter.)

I have a set or Ortlieb rollers, front and rear, on Tubus racks, with an Ortlieb handlebar bag. I've lived out of them for around 4,000 miles of loaded touring over four years. Including three, one month solo tours.
This set up carries everything I need to live on the bike for an open-ended amount of time without needing a stack (which is anything strapped on top of the rear rack; although it's good to have the option)

At the same time, the combination of small front bags and handlebar bag allow for a set-up to get me through smaller trips. Just going out for a long day? The handlebar bag and one front bag attached to the rear rack- allows me to carry everything I could possibly want or need. And overnight with no cooking? The two small bags and the handlebar bag suffice.

I would not recommend the larger rear rollers for general use, They are massive and don't close well without something in them.

So I'd recommend starting with a pair of front rollers or similar, and pick up the larger rear ones when you're ready to head out for an extend time.

This is such a versatile set up, I can't imagine needing or wanting anything different, Unless I decided to do more off road bikepacking. In which case, I'd want a different bike and different bags to put on it. Because bike packing is a totally different approach that requires different equipment.