TOPIC: "roll out " & "roll in"

Normally, we say "to roll out a new plan". The dictionary explains this as
" to make a new product, service or system available for the first time".
However, I also notice some people use "a roll-in plan" in their presentation. This doesn't look like a typo error as it was mentioned in many places.
Is there any difference between roll-in and roll-out? Should we say "to roll-out a new system" or "to roll-in new system"?

Yes, you are right in saying that "roll out" is used to mean launch a new product, system or service for the first time. So, a "roll-out plan" is a plan for how the new product will be introduced.
I haven't been able to find a specific reference to "roll something in" (as in your example,"a roll-in-plan"), so I suspect that it results from a combination of "roll out" and "phase in",perhaps with the sense that the new product (or system or service)will be introducted in stages(i.e., phases) rather than all at once. I'll keep looking for any occurences of this phrase and post it here if I come across it.
In the meantime, you might want to check out this page, which gives quite a detailed list of meanings and phrases with "roll"(but alas, no "roll in" except for the meaning "arrive", as in "He just rolled in last night at 1:00 a.m."):
dictionary.reference.com/search?q=roll