Roseanne's Ex -- 'She's Worth $42 MILLION' ... Demands Lawyers' Fees

Roseanne Barr's ex-husband is demanding $75,000 for attorneys' fees, and another $100,000 for dragging him through a child custody battle -- and he claims that's a tiny fraction of her $42 MILLION fortune.

Ben Thomas filed legal docs today demanding that massive amount of money ... in the wake of their extended custody battle over their teenage son, Buck. The exes reached a settlement back in August -- but Thomas claims Roseanne's efforts to strip him of custody were only motivated by revenge ... hence the demand for $100K.

In the document, Thomas points out the $100,000 is a mere .002% of Roseanne's net worth of $42 million.

By the way, Thomas claims he earns $7,305 monthly ... compared to Roseanne's $211,667 per month.