Quoting Lady GooGoo™:" Zoey is 5 months now. All she does as far as mobility is roll rom tummy to back a grand total of 3 times ... [snip!] ... DD1 was starting to sit up as well. DD2 is just not interesting in moving around yet, lol. Which is more than fine with me."
DS is like this.
He rolls from tummy to back but barely... He does not sit up unassisted and doesn't even try to... He is a big immobile baby lol
Most people only come to these type of topics to brag (albeit: you asked) so whatever people are saying their five month olds are doing -- it isnt the norm for most babies.