I am a Roces EXPERT !!
They make a total of 3 different size boots .....each boot adjust 4 sizes.
I have been able to use those different boots from age 4 to right now ---age 11.
I think my oldest can use the largest boot (this year) at almost the highest setting.
I can usually stretch 2-3 seasons out of one adjustable boot.
I bought all the Roces used ---my kids ski 30-40 days a season.
We ski Whiteface - the oldest can ski the Slides - the other 2 can ski Skyward.
The kids can rip and the boots, more than hold up.
All 3 will be using the largest size Roces this year.
Next season - at this point - I think we are leasing.
ADKMike - i have some boots the kids out grew - happy to give you what you need
DM if you are interested.
This is what I have .........
Roces Adjustable Ski Boots - 1 Pair - size 16.0-18.5
Roces Adjustable Ski Boots - 2 Pair - size 19.0 - 22.0
https://www.roces.com/en/winter-sports/children-adjustable-ski-boots.html
Full Tilt Adjustable Ski Boots - 1 Pair - Size Small = MP 18 - 21.5
https://www.getboards.com/full-tilt-growth-spurt-adjustable-kids-ski-boots-2018/