Retirement tax questions

An informative dialog so far. A new wrinkle: The adviser who comes gratis with our 403b told us that we could not take our minimum required distribution as a Roth conversion. Hence, if x is our MRD, then a Roth conversion y results in taxes of both x and y. It is very difficult to find this sort of discussion on "google" - dozens of ads and teasers from financial advisers.

 

So 2 questions for our assembled experts: is the above advice (MRDs and Roth conversions must be separate and both taxable) on 403b accurate? Same rule for distributions from IRAs? Thanks -