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There is totally a Roadside Picnic RPG. It's called STALKER, just like the movie, and is a kinda crazy RPG with some pretty neat ideas in it.
You can read about the game over here: http://www.burgergames.com/stalker/EN_web/
Also, to answer your more general questions: new players are welcome all of the time. Lots of gaming stores hold open events specifically designed to let new players try out RPGs. Anyone that gives you an "Ugh, filthy newbie" attitude is a dick and you should take you and your good gaming to a different table.
Most of the older generation of gamers would suggest starting with some variation of DnD, like 3.5 or Pathfinder. They make this suggestion largely because that's where they got their start and its seen as a rite of passage for most gamers to play DnD. I say "fuck that".
That's not to say that those games are bad. They aren't. It just sounds like you have interests elsewhere. Don't seek out a DnD game, seek out an interesting one. Just like movies, comics and books, there's all kinds of great games out there to play. Don't feel like you need to limit yourself to the same experience that everyone else has had. Find a game that you're interested in, that you think sounds fun, and use that as your first experience.
You like post-apocalypse? Hunt down Apocalypse World or the aforementioned STALKER; two very different takes on the same themes. Mecha? Howsabout Mechwarrior, or Mekton Zeta, or MECHA, or Bliss Stage, just to name a few. Cyberpunk is so loved that there's a cyberpunk RPG simply called Cyberpunk (go with the 2020 edition, there). If you like your cyberpunk a little weird, grab Shadowrun to add magic spells and fantasy races to your peanut butter, or Eclipse Phase if you want to step sideways from cyberpunk to transhumanism. High fantasy... man, there's too many to count, but just let it be known that DnD is simply the tip of the iceberg there and, depending on your tastes, may not even be the best high fantasy game for you.
So, there's lots of game. Lots. And there are people in this community kind and generous and welcoming enough that you'll be able to find a table with very little effort. Go out there. Find a game and play. And let us know how it goes when it's all shaken out.