Roaming has become a popular addition to the metagame strategy, wherein one player does not lane nor jungle, but rather simply moves through the jungle/river to initiate ganks on lanes from level 1 and onward, until the teamfight portion of the game begins.
A roamer essentially guarantees that you're either running a solo lane, or two solo lanes if you have a roamer and a jungler. I've also seen a double roamer game played, though this tends to be less effective as enemies who are wise start playing defensively and reduce the effectiveness of your roamers, which put them behind in both CS and levels.
The qualities of a roamer can vary, but the general requirements are that they are mobile, can do burst damage, and have a strong stun or position altering (push, throw, etc.) ability. Taric, Evelynn and Alistar are all very popular choices for roaming. I've also seen Sion and Blitz play roaming effectively, but they were both out of a lack of a jungle spot on the team and normally suit better in a lane.
This strategy is similar to the "double jungle" mindset in that you get three solo lanes, with the exception that there is extra pressure on getting early kills to succeed. A definite risk vs. reward tossup, as successful roamers will quickly catapult your laners ahead in level / CS as well as demoralize your opponents, but unsuccessful roamers will fall just as far behind due to the lack of their presence in the laning phase.
The best option is to go premade with people you know.
If you solo then yes you should ask people what builds are they using and what lanes they want to be in,people will often be ok and tell you how they plan to play the game,but of course there are times when you just get people that want to troll and there is nothing you can do about it.
Personally what i sometimes do when i enter solo queue is that i type in:"STOP DON'T LOCK IN" as soon as i enter queue,and people often listen and do not lock it after that,and then i tell them that we should build our team carefully and most people are ok with that.
Of course some people get rude about it and lock in with random champion and there is nothing you can do about them,either dodge queue or stick with them and hope for the best.
I would also mention that even if you get really weird team combination that you can still win if you're lucky.Even if your team may have crappy combination there is a chance that enemy team doesn't have good combination either or that they don't know how to play their champions so good.So there is always hope.
Best Answer
To directly answer your question, 'ss' is a shorter version of 'miss'. In certain regions, they differentiate between this and "MIA", which is meant to refer to a specific opponent whose location is not known rather than a lane with missing people.
From a forum post:
On North American servers, people tend to use mia for both purposes: