Johanna Rosaly was born in Santurce, a district of San Juan. In 1956 at the age of eight, she started taking acting lessons with Argentinians Luis A. Negro and Elba Mania, and dancing lessons with Beatriz Trujillo. In 1957, she made her acting debut as a child, on stage, at Teatro Tapia, in Old San Juan, in Mientras los Ninos Juegan (While the Children Play). That same year, she made her debut on television, with channel 2's children's production of Los Amigos de Pinocho (Pinocho's Friends) as well as in the film Con Los Pies Descalzos (an Osvaldo Aguero production, starring the Catalan actor Ricardo Palmerola).
Rosaly started taking singing lessons when she became a teenager. Then, she participated on stage in zarzuelas such as El Caserio (The Country House), and Black el Payaso (Black the Clown); operettas, such as La duquesa del Bal Tabarin (The duchess of the Bal Tavern), and musicals performed in English, such as My Fair Lady and The Sound of Music. The latter, allowed her to perform on stage with another Puerto Rican acting legend, Camille Carrion.
In 1966, already in her early years in college, she made her TV debut in the telenovela El Retrato de Angela (Angela's Portrait), broadcast by Telemundo. In this soap opera, she played a mute girl. Later, she married her first husband, Puerto Rican film director Jose Gilberto Molinari. They procreated 2 sons and a daughter. Alfonsina Molinari is Johanna's daughter and she is an actress and an opera singer.
During the 1970s, Johanna Rosaly had a short but notable career as a singer, and she signed with the Velvet Records label, and began touring all over Latin America, to promote her two albums under that label. She also attained considerable fame in Spain. Later, she would sign with CBS International label, now Sony Discos, and recorded two more albums for them.
Rosaly performed in 15 soap operas altogether from 1966 - 1980. However, the leading roles she is mostly remembered for were, 1973's El Hijo de Angela Maria (The Son of Angela Marie), alongside Rolando Barral, Mona Marti, Angela Meyer, and Lucy Boscana, among others. This performance led her to carry out the same leading role, Marisela Perdomo, in the film based on the telenovela, in Mexico, opposite Iranian-Mexican actress Iran Eory, and her crossover as a singer and actress was, 1978's Cristina Bazan, opposite Jose Luis Rodriguez "El Puma", and alongside Alba Nydia Diaz, Esther Sandoval, and Adamari Lopez, at the early age of 6, among others.
In 1979 moved from WKAQ-TV Telemundo Puerto Rico to WAPA-TV. There, she performed the leading role in the 1980 soap operas: Vida, (Life), & Amame, (Love Me), opposite Andres Garcia, for which she sang the theme songs "Yo Soy un Barco" (I'm a Ship), and "Amandote" (Loving You), respectively.
in 1980 she starred in El Amor Nuestro de Cada Dia (Our Daily Love), in which she also sang the title song of the same name, composed by Lou Briel.
As the 1980s came about, Rosaly made a short parenthesis in her acting career, working as an executive in WAPA-TV, and shortly, moved to Telemundo again, and became an entertainment anchor woman and host in the talk-show, En Vivo a las Cinco, (Live at Five), and in the game show Super Sabados, (Super Saturdays) for several years.
In 1989, she performed alongside Tommy Muniz in the motion picture film Lo que le Paso a Santiago, (What really happened to Santiago) produced and directed by Jacobo Morales, which was nominated for an Oscar as the best foreign film. In 1993 she performed in, Shortcut to Paradise, and in 1994's Linda Sara, (Pretty Sarah) alongside Chayanne and Dayanara Torres.
During the 1990s, she was dedicated mostly to act on stage in several theater productions acclaimed by the critics, such as her impersonation of Maria Callas in Master Class, among many others, and since 1993, Johanna's been working for WIPR-TV channel 6, Puerto Rico's Government TV channel, (Tu Universo Television), hosting several talk shows, among others, Mucho Gusto (It's a Pleasure).
In 2010, she made her debut on the New York stage, in Sabina y Lucrecia. Rosaly and New York-based actress Eva Cristina Vasquez starred in this play by Alberto Adellach, " a tale of two very different mentally ill women who escape an asylum."
Presently, she hosts ¿Y como fue? (And How Was It?), and Cultura Viva, (Alive Culture), alongside Puerto Rican actress Cordelia Gonzalez. She is also the lead researcher, scriptwriter and narrator of the program, and is credited with its conception.
On January 11, 2008, Rosaly married Jose Manuel Saldana, the former president of the University of Puerto Rico. The couple announced their separation in June 2011.
Rosaly played "Mrs. Warren" in the San Juan revival of La profesion de la Sra. Warren, as part of the International Festival of the Puerto Rican Culture Institute.
She has received multiple honors, among them, the Puerto Rican Culture Institute (ICP), dedicated their 1997 International Theater Festival to her, honoring her more than 40 years as an actress.