To my knowledge, everyone under this page's "Tekijät" section: http://www.radiohelsinki.fi/ohjelmat-tekijat/
Some of them are fairly big names in Finnish rock, and the station itself is pretty well known.
Is that the music staff? If so, that's impressive. And if it's a list of the people who voted in this particular poll it's even better. With "big names in Finnish rock", do you mean well-known artists or radio hosts?