Is this your first child? First children often miss a few milestones, especially if Mommy stays home with them instead of day care, because they don't see anyone else their size doing new things. They'll watch Mommy and Daddy walking, and eventually get the idea, but the second child will pick it up a little faster, because that child will be able to watch their older sibling all day, every day, and get a better idea of how to do things when you're only two or three feet tall.
My eldest daughter was much the same walking-wise; she wasn't really walking unassisted until just before her second birthday, while my middle daughter got the hang of it around her first birthday. However, my older was a real babbler, and started learning the names of things in her daily life fairly early, maybe about 8 months or so. My middle child's been slower to learn language, and at 18 months she still has a fairly limited "signal word" vocabulary (mommy, daddy, blankie, milkie, cookie, hung'y, phone, up, down, maybe a couple others) while my elder child was really taking off by that age, with parts of the body, furniture/appliances, and basic times of day.
Your child will start doing these things when he figures out the advantage of doing them over what he's currently doing. He learned to roll over because it was boring to lie on his back and stare at the ceiling (and/or it was tiring to be on his stomach holding his head up for so long, then unpleasant to lay his head down in his own drool). Then he learned to crawl because he couldn't reach something he wanted on the floor from where he was, and he learned to pull up and cruise because it changed his perspective of the room allowing him to see further. When he realizes that walking allows him to move more quickly, and/or to carry something in his hands while moving, he'll start trying harder to master that skill. Similarly, when he learns that words are symbols, not signals, he'll want to learn the words for more things so he can say what he wants in more situations.
One thing my wife and I think may have jump-started our eldest to learn to walk was to soften the floor. Practically all the floors in our house are hard surfaces (tile, laminate etc), and on a hunch we bought a big area rug for the living room where she spent most of her day crawling and cruising. Within a month after that, she was walking. It may be coincidence, or she may have realized the rug doesn't hurt as much to "fall down go boom" onto, which increased her confidence in trying to walk.