Roth 401K question

I am a 47M (married, joint accounts/balances) with 4M in total assets and roughly 2.5M in 401k or roll-over IRAs (i.e. all tax deferred)

My goal is to retire at 55. Should I be switching my ongoing 401k contributions to Roth 401k? I only recently learned my company offers that as an option and I don't truly understand the implications of doing so. My fear is that my tax deferred balances will be quite large and my RMDs and tax burden when I'm 73 will be significant.