IKHYF as Mason hadn't even rolled over at 6 months. I was freaking out as he was the only one in our mothersgroup that hadn't. Once he got the roll he was quick to crawl, and stand at the couch etc. He was walking at 12mths.
Angus was rolling at 4 months but then didn't walk till he was 14mths.

My Dad didn't walk till he was 2!

They are all so different and do their thing in their own time. Please don't stress about this too much you're doing a great job