In December, seven people died in an explosion in Yazd. On November 28, a bomb seems to have gone off in nuclear facilities in Isfahan. On November 12, 17 people were killed by an explosion near Tehran. On July 23, a scientist called Darioush Rezaeinejad was shot through the throat outside his daughter's kindergarten. On November 29, 2010, Majid Shahriari was killed in the same way as Roshan, with a bomb planted in his car. Fereydoun Abbasi-Davani was also attacked, but survived. On January 12, another motorcycle bomber killed Masoud Alimohammadi.[abc.net.au]
If the purpose of the action is to create terror, then the act is terrorism. If the purpose is action is to eliminate a utility and the terror is incidental, than it may just be an expedient methodology. The level of physicist that could legitimately aid in development of a nuke program is always in short supply and difficult to replace which makes them legitimate targets, and who knows how convoluted a plan has to be to be effective in this particular environment. It might be terrorism, but the fact that they're using explosives on these so-called 'civilians' and that there may be collateral casualties, in and of itself, certainly doesn't make the case that it is.