Go for it!
I'm in my 50s and have rollerbladed since my early 40s

It was scary at first because rollerblades go A LOT faster than the 4-wheelers I grew up on! Amazingly, I have NEVER fallen. Weight should not be an issue, as long as you're wearing adult skates
I've been very tempted to bring my skates to school, so that I can get around a lot quicker (or maybe I should buy those shoe-skates...)
I would suggest to get padded up (knees and head, esp. and don't forget your rump!).... I know, I know, you'll probably look like a roller derby queen, but who's going to know who you are with all that gear covering you up?
Start out in the grass to get a "feel" for the way you need to stand. I think the important part is to make sure your ankles have good support, so you're not bowlegged (in or out). You might also try out your skating on carpet. I remember "zooming" around the sports store (where I tried on the skates) on their carpet. That gave me more of a feel and confidence.
Lastly, I practiced on flat cement surface in front of my house. The street was smoother than the sidewalk. I went VERY SLOWLY and picked up more speed when I felt more confortable. It took awhile for me to learn how to stop and make turns that didn't go around the whole block!
Go for it and you'll develop confidence. WANTING TO TRY is the first step! Just be careful to avoid the small rocks that could jam the wheels and cause a problem. Have fun and let us know how your "maiden flight" is!
LindaR