What are the roles of government.?

This is definitely a debatable issue. However, here's my take:

It is the government's role to evaluate the issue of Immigration through the lense of the people's will, the lense of national security, and the lense of historical precendent, and economic stability (to name a few)...

It is then necessary for the government (specifically each member of congress individually) to determine what laws (if any) need to be passed/repealed to better regulate/de-regulate immigration activities in order to insure that the people's will, national security, past immigration activity, economic stability, along with a host of other concerns are adequately accounted for. Propose new laws if necessary, vote on these proposed laws and allow them passed into law if agreed upon. Them the executive branch must enforce these laws, and the judicial branch must uphold these laws in their judgments.

As for non-government organizations, really there only role is to abide by any such laws. One might argue that businesses who cater to the cheap labor of immigrants are not being responsible. However, so long as the business are not breaking the law in their employment practices, they are within their legal right to do business.

I would argue that our current situation is a result of a failure to act on the part of government organizations in order to insure the integrity of our economy and adequately address those concerns above, particularly as it relates to the enforcement of violations to illegal immigrant employment and minimum wage laws.