It seems to me Michael was no different to Vito in conducting their business

Both Vito and Michael were the same evil, ruthless, murderous Dons

The ever astute Roth would have always remained a lethal enemy, plotting to kill Michael and that Tom couldn't / didn't see Roth as such - Kill or be killed – reinforces Tom is a good lawyer not a Sicilian no wartime Consiglieri

Michael after establishing himself as the Top Mafia Don and then masquerading as 'legitimate' businessman, Michael was only reactive
ie: “They hit us So we hit them back”

Vito among others -

• killed Don Fanucci and took over his business [Granted Vito looked after the people as well unlike Fanucci] Moe Greene was made an offer no such offer to Fanucci
• threat of lethal force - band leader's signature or brains even in such simple business as his Godson Fontane's contract release
• killing of defenceless Khortum horse
• went back years later and killed, a senile, one leg in the grave, Don Ciccio who was living out his last days thousands of miles away absolutely no threat to the Corleones - vengeance for killing his family because the enemies have to be wiped out
• planned all the dirty work - killing of Carlo Rizzi and Moe Greene, the baptism murders - for Michael to carry out after Vito's death thus leaving a murderous legacy for “I never wanted this for you” son Michael

I think it was Turnbull who posted Michael wanted to be the biggest legitimate gambling operator in the Western Hemisphere or similar
So following on, no longer “like the Roman Empire”

I agree Tom can only leave Michael's side....in a box!