The 2006 Kennedy Center's premiere of Missa Latina was a stunning success. Like a spontaneous eruption, the audiences that attended the three performances jumped from their seats to cheer the work. T. L. Ponick from the Washington Times wrote: "...the most significant symphonic premiere in the District since the late Benjamin Britten's stunning 'War Requiem'... Mr. Sierra's new work is, quite simply, shockingly brilliant..." Following the Washington success the Casals Festival programmed the work for a second performance last March (2007) with equally enthusiastic responses from the audience and the press. Missa Latina was also performed in Hawaii where the Introitus, Sanctus and Agnus Dei were performed at the Honolulu Symphony Orchestra's end-of-year concerts (December 29-30, 2007) conducted by Andreas Delfs. The Houston and Milwaukee Symphony Orchestras, as well as The Los Angeles Master Chorale have programmed the work for the 2008-2009 season.

Roberto Sierra is one of the nine composers commissioned by philanthropist Kathryn Gould (Meet the Composer Magnum Opus commissioning project), to write new orchestral works for three different Bay Area orchestras: The Santa Rosa Symphony, The Marin Symphony and The Oakland East Bay Symphony. The five movements of Carnaval, the new work Sierra wrote for this project, allude to imaginary and mythical creatures: Gargoyles, Sphinxes, Unicorns, Dragons, and The Phoenix. About the Oakland East Bay Symphony premiere on April 18th 2008, San Fracisco Chronicle critic Joshua Kossman wrote: "Like the Schumann piano piece from which it takes its name, 'Carnaval' is a collection of character sketches, in this case a bevy of mythical creatures...The result is a breezy, fresh-sounding entertainment that moves nimbly from one section to the next and keeps the listener engrossed throughout...[Sierra] fleshes out those ideas with ingratiating melodies and a masterful orchestral range."

The Cleveland Orchestra under the direction of Giancarlo Guerrero performed Fandangos at Severance Hall as part of their subscription series on March 20, 21 & 22, 2008. Following these performances the orchestra took the work on tour to Florida - St. Petersburg (March 24), and Miami (March 28 & 29), and to Columbus, Georgia (March 30). Donald Rosenberg from the Plain Dealer wrote: “The piece is an explosion of zesty variations on a tune by Antonio Soler -- an old form tweaked by contemporary inventiveness... the percussion made striking contributions, the bassoons rumbled with glee, and the violins provided Spanish bravura bowing vibrantly across their strings.” Elaine Guregian commented in the Akron Beacon Journal: “The orchestra played Fandangos, composed by Roberto Sierra in 2000, at the Blossom Festival in 2002. Sierra’s captivating piece opened the program on Thursday, and it’s easy to imagine it being brought back again soon. Sizzling trumpets, curvaceous oboe lines and some seriously catchy dance rhythms...”

After a highly successful premiere tour that included Atlanta's Spiviey Hall, Maryland's Clarice Center and the Herbst Theater of San Francisco, soprano Heidi Grant Murphy accompanied by pianist Kevin Murphy and the St. Lawrence String Quartet gave the NYC premiere of Songs from the Diaspora at the Chamber Music Society of Lincoln Center. Jay Nordlinger from The New Criterion wrote: "In CMS’s program notes, Christopher Costanza, the St. Lawrence cellist, wrote something interesting. You could even say that he confided it. Originally, he said, the SLSQ ‘programmed the piece in that safe ‘new music’ slot, before intermission, with meaty, intense quartet repertoire filling the second half.” But when they spent a little time with the Songs, we realized that we had a true tour de force on our hands—a beautiful, varied, inspired, creative, and memorable work nearly 30 minutes in length. There was only one place on the program for such a profound work, we decided: it would have to close the program. What a huge compliment to Roberto Sierra that his remarkable new piece has proven to be, over several performances... , a fully successful program closer!’... And I can endorse what he has said about the Sierra work: It is beautiful, varied, creative...There are a lot of Sephardic songs in the world...and Sierra’s work deserves a proud place among them.”

Sinfonía No. 3 "La Salsa" was received with standing ovations after its premiere performances in Milwaukee, and was released by the Milwaukee Symphony Orchestra conducted by Andreas Delfs on its e-label MSO Classics, now available on iTunes. Milwaukee Journal Sentinel critic Tom Strini described the work as: "fantastical, witty and brainy as one of those Matisse still lifes, ... engages on many levels, and the Friday matinee audience stood and cheered the work and the composer..." In a review of the MSO release on ClassicsToday.com Joseph Stevenson wrote: "The work is not just a dance piece masquerading as a Symphony; it's the real thing ... The Salsa Sinfonia is a major addition to the repertoire..."

Within a month of its May 2007 premiere in Valladolid's newly built hall with the Spanish Orchestra of Castile and Leon and soloist Manuel Barrueco, Danzas Concertantes for guitar and orchestra received two additional performances at the Koblenz (Germany) and Cordova (Spain) International Guitar Festivals. On February 2008, Barrueco played the American premiere of the new concerto with the New Jersey Symphony (click on Reviews to read what the critics had to say)