Bring Your Fiddle, If You Like
"Better to live on a corner of the roof than to share a house with a quarrelsome wife." - Proverbs 21:9
That's not my problem, but if it's yours, I'm sorry.
I'm not sure if that proverb is the source of Sit on a Rooftop Day or not, but it sounds like it could be.
But assuming you don't have (or aren't) a quarrelsome wife, you can still celebrate this day fairly easily, as long as you have (or can find) a rooftop within reach.
Our roof is rather difficult, but not impossible, to get to. I have to take my special bend-it-anyway ladder up onto the small deck and lean it against the house/roof in the shape of an L. Then it's a simple climb to the top.
I don't see any minimum amount of time that you have to stay of a rooftop in order to celebrate the day. So it's not like you have to sit up there all day. A few minutes should suffice.
Also, it apparently doesn't have to be the roof of a house. The roof of a car or other vehicle should work just as well. Be careful though - some of these aren't all that sturdy these days.
If you make it onto the roof of your house, you might as well look around to see if anything needs fixing. When was the last time you actually checked your roof for problems. Is it leaking into your attic, and you didn't even notice?
"A quarrelsome wife is like the dripping of a leaky roof in a rainstorm." - Proverbs 27:15