My spouse is a Nebraska Resident working in Nebraska and I am Iowa resident working in Iowa. If we file jointly for federal, do I have to file returns for Nebraska?

No, if you do not have to file if you did not have any Nebraska source income.According to the Nebraska Information Guide, page 4, you may file a married filing separate returns (if one spouse is resident and the other spouse is nonresident) even if you filed married filing jointly for the federal return.  The nonresident spouse need only file a married filing separate return when he or she has Nebraska source income.  http://www.revenue.nebraska.gov/info/8-645.pdf,,

Married, Filing Separately. Married, filing separately Nebraska returns may be filed when one taxpayer is a resident or partial-year resident while the other taxpayer is a nonresident and, although a married, filing jointly federal return was filed, they did not elect to file a married, filing jointly Nebraska return. The resident taxpayer must file a return when he or she receives any income, regardless of where that income is earned. The nonresident taxpayer must file a return when he or she has Nebraska source income

You can also elect to file a married filing jointly Nebraska return.