Can we file state MA return as married filing jointly and RI married filing separately? Federal return is MFJ. We both reside in MA but my husband works in RI.

No, Rhode Island requires a joint return.  The only time Rhode Island accepts a Married Filing Separately return is if one of the spouses is a RI resident and the other is not.  Since you are both Rhode Island nonresidents you will file a joint return in RI if you are filing a joint return for the Federal Return.  

However, while it may be a requirement to file a joint return, Rhode Island can only tax the income earned in Rhode Island.  And, on the Massachusetts return, you will receive a credit for the amount of tax you must pay to Rhode Island on the income earned there.

Please note this excerpt from this website Rhode Island State Taxes and Rhode Island Income Tax Forms (click on link for additional information) :

In most cases, the same filing status is used on your Rhode Island tax return as on your federal income tax return. However, there are exceptions to this rule, but these are rare and rather extreme. For instance is you are married filing jointly with a spouse who is a part-year resident, your filing status may vary from your filing status used on your federal income tax return.