She is slender and lanky, with a long neck.
Rosil is one of three Yellow sisters who accepts Nynaeve al'Meara as a full sister before she is actually raised. She explains to Nynaeve that she has been so welcoming because she is impressed with how effective Nynaeve's new weaves are.
She leads Nynaeve to her test to become Aes Sedai, where she allows Nynaeve to break custom by allowing her to leave her Great Serpent ring on the finger of her choosing and by allowing her to speak. When Nynaeve finishes her raising test and returns from the ter'angreal, Rosil Heals her. She then stands aside as the Sitters debate whether Nynaeve actually passed the test, and concludes the ceremony as tradition dictates when they have made their decision.