My take is, killing Michael in Havana is not as risky as Tahoe bedroom shooting In fact, Havana was a sure winner!
Havana plan was “brilliant” I believe foolproof [unlike Tahoe] and Roth's “golden opportunity to get rid of Michael” without anyone even suspecting Roth – Michael's terribly unfortunate death

As regards Roth's “critical blunders” -
  • Roth was slipping! Roth overthought! a simple murder
  • Roth banking on Pentangeli making the perfect patsy for the Tahoe shooting – too many variables
  • I now don't quite understand why Roth needed to “set up the Rosatos to take over NYC” because once Michael is murdered in Havana there was no need “Nobody wants another war”

My revised view! I now believe Roth was not a greedy man, for Michael's business nor the $2 million
Michael had to make an investment [$2 million] in Havana not dissimilar to the other investors

I don't think “he [Roth] held out way too long” to whack Michael in Havana
I believe, Michael's any unexplained violent death other than the meticulously planned, carefully considered and arranged, after the New Year's Eve Presidential party, caught up in the midst of the rebel uprising in spite of being escorted in a military car, can be fraught with problems, not as 'believable' and would certainly raise suspicions why Michael was the only one killed

if there was no Tahoe murder attempt -
  • There would have been no Michael and Roth “are on to each other”
  • Michael would have arrived in Havana with the $2 million, eager to be anointed as Roth's heir apparent and handed the money over to Roth
  • Michael would have ended up never seeing the New Year

Roth played Michael beautifully, had Michael "dancing on the strings" held by Roth, had Michael believing Roth loved Michael like his son, Michael was Roth's heir apparent and Roth was 'gifting' his business to Michael - until the Tahoe shooting
All of the above and of course greed blinded Michael

Revenge blinded Roth