ds2 is only just 6mo.. he is already miles more active than his brother at this age. ds1 i don´t think EVER rolled off the sofa or bed, he barely rolled at all only really getting into it, in his now trademark laconic manner, about 9/10mo. I can´t remember when he crawled, probably about the same time, and walked at 15mo. All in all it was rather handy as he tended to stay where I put him and not get up to mischief.
ds2 is almost, but not quite, sitting unsupported and recently pulling his knees right up under his tummy (when on his front) and supporting himself on his elbows! I am terrified our relative peace is about to come to an abrupt end does it sound like he is about to crawl or could he be doing this for ages yet (hoping and praying for the latter!)
DD2 is 7 months this week and in the last month or so has gone from commando rolling to commando crawling - and she's quick - especially when she sees the cat! She will go on all fours and push her bottom up into the air and do that back and forth rocking motion thing so I've no doubt she'll be crawling 'properly' very soon. She's been pulling herself up to stand for several months - loves just standing and looking around. I'm having to get a new fire-guard far sooner than I'd imagined!