Nascent Psyker and sustained powers

By Inquisitor Kleeves, in Dark Heresy Gamemasters

I ran into an issue of a guardsmen going psycho with chameleon...now the one minor power that nascent psykers get can be used automatically without making a power roll and without generating psychic phenomena...so when using sustained powers do they hold untill their done or do they still need the second and third and so on power rolls to continue sustained powers?