Direction beats level: a 22% margin rising from 18% and a 22% margin falling from 30% are different companies. Incremental margin — change in EBIT over change in revenue — tells you the economics of the next dollar, which is what you are actually buying.
ROE is flattered by leverage and by buybacks that shrink equity; ROA is cruder but harder to game; ROIC (NOPAT over invested capital) is the central quality metric. Incremental ROIC — the return on new money over three to five years — determines whether growth creates or destroys value.
The rule that governs everything: growth creates value only when ROIC exceeds WACC. Below it, growth destroys value and every retained dollar should have been paid out. A fast-growing company earning below its cost of capital is one of the most reliable short archetypes, because the destruction compounds.
Educational, not investment advice.