Antonyms of adj roily

1 sense of roily

Sense 1
churning, roiling, roiled, roily, turbulent -- ((of a liquid) agitated vigorously; in a state of turbulence; "the river's roiling current"; "turbulent rapids")

INDIRECT (VIA agitated) -> unagitated -- (not physically disturbed or set in motion)

Similarity of adj roily

1 sense of roily

Sense 1
churning, roiling, roiled, roily, turbulent -- ((of a liquid) agitated vigorously; in a state of turbulence; "the river's roiling current"; "turbulent rapids")
       => agitated (vs. unagitated) -- (physically disturbed or set in motion; "the agitated mixture foamed and bubbled")