Dzhokar Tsarnaev, the surviving plotter in last year's deadly Boston Marathon bombings, kept his cool in the days after the attack, a former college roommate testified Tuesday. "He slept a little bit more, but that was it," Andrew Dwinellis said, adding that although he and Tsarnaev shared a room, they did not talk much or hang out together.

Dwinellis' testimony came during the trial of Azamat Tazhayakov, a friend of Tsarnaev's charged last August along with two others with conspiring to obstruct the bombing investigation.

Soon after the FBI posted pictures of the alleged bombers, Tsarnaev sent a text message to one of the friends, telling him to go to Tsarnaev's "room and take what's there." Tazhayakov and the others "removed several items from the [dorm] room, including Tsarnaev's laptop computer and a backpack containing fireworks," prosecutors say. The conspirators placed the materials into a backpack which they threw into a dumpster outside their New Bedford apartment

In his testimony, Dwinellis confirmed that co-conspirator Dias Kadyrbayev came to the dorm room and "said he needed to get into the room to get something." After pulling out a small bag of marijuana from the desk drawer, Kadyrbayev searched the room for another 10 minutes. While Kadyrbayev searched the room, Dwinellis said Tazhayakov and another friend sat and watched television.

During Monday's opening statements, prosecutors said that Dzhokar Tsarnaev told Tazhayakov that he wanted to die as a martyr one month before the bombings that killed three people and injured 200 others. Tazhayakov reportedly told the FBI that during dinner at a North Dartmouth restaurant, Tsarnaev told him that he knew how to build a bomb and "it was good to die a martyr as you would die with a smile on your face and go straight to heaven."

Tsarnaev's brother Tamerlan was killed in a shootout with police days after the bombing attack.

Tazhayakov and Kadyrbayev, who is scheduled to be tried separately in September, face up to 20 years in prison if convicted. Prosecutors are seeking the death penalty for Tsarnaev, who is scheduled to go on trial in November on a 30-count indictment for his role in using improvised explosive devices constructed from pressure cookers at the April 2013 Boston Marathon.