My take, for what it is worth!

Why would Roth [or Michael] need insurance policies?

Nobody other than Fredo and us, the Godfather scholar! Board members knew about Michael and Roth's murder plots of each other

Neither Tom, Neri nor Rocco had any idea and were totally in the dark about - if my memory serves me right, among others,
  • It was Roth who tried to kill Michael in the Tahoe bedroom shooting
  • Roth's plan B to murder Michael in Havana
  • Roth's “anointing" of Michael that Roth “was gonna turn over his entire Havana gaming empire to Michael”
  • Fredo was the traitor in the family
  • Frankie Pentangeli was alive
  • Roth's Plan C – Senate hearing in which Willie Cicci had already been grilled
  • Senator Geary was no longer in the Corleones' pocket

If Michael had died, it would seem such a terribly unfortunate death, caught up in the midst of the rebel uprising in spite of being escorted in a military car

If Roth had died smothered by a pillow it could seem a natural death caused by Roth's stroke

So, I believe, neither Michael nor Roth 'needed' insurance policies Whom did they have to answer to? Everyone none the wiser