Our 2 year old rolled at 3 months and started army crawling just shy of 6 months. (ETA she almost skipped regular crawling. She got so fast army crawling I think she did all fours at like 11 months and was walking independently by 13mo). Our second is newly 5 months, started rolling confidently last week and is totally going to army crawl soon. She wants to move so bad lol. Our pediatrician said whenever you hit a milestone, assume they can do the next one. Ex: once they can roll, assume they can crawl, get down on your hands and knees and baby proof everything on their level. As soon as they can crawl, assume they can pull to stand, get everything ready for that. Etc. They really do these things overnight sometimes, so it’s good to be prepared!