Relation between Rollet stability factor and Bode plot

Dear All,

While designing opamps, one deals with phase margin for stability. But when designing LNAs, Rollet stability factor is checked. I am sure these two are related but for some reason Rollet stability factor is more appropriate for LNAs.

1) Can someone shed some light on the relation between these two?
2) Why Rollet stability factor is more appropriate for LNA and not Bode plot?

Thanks