'The Conners' Star Michael Fishman I'm Separating And, Not Getting Divorced Because ...

Michael Fishman, famous for playing Roseanne Barr's TV son, says one of the big reasons he and his estranged wife chose separation over divorce is simple -- he'd like to keep her on his health insurance plan as long as possible.

 "Among the reasons for not getting a regular divorce is the shared desire to keep Jenny [Briner] covered by my health insurance, and allow to slowly unfold our 20 years together in a way mutually beneficial for our family, particularly on behalf of our children."

Jenny filed docs Thursday for legal separation after more than 19 years of marriage. Michael told us the decision to split was an amicable one ... adding he, Jenny and their 2 kids actually went to the courthouse together and afterward had a family dinner.

Legal separation's usually a stop before a divorce ... but Michael wouldn't say whether they'll ultimately travel down that road. As for what led to the separation, Michael wouldn't say ... but keeping things amicable with Jenny is important to him ... and it clearly shows.