Both Fullarton and Roget signed with The Bees on a non-contract basis last month and both have had their deals extended with the Division Two leaders.
Fullarton has agreed to a year-long contract while Roget has signed a four-month deal until the end of December.
Defender Ben Chorley - who is on loan from Premiership champions Arsenal - has also agreed to an extension of his loan deal to three months with the Griffin Park club from his original one month deal.
Meanwhile, the shoulder injury to Icelandic goalkeeper Olafur Gottskalksson (pictured) has turned out to be more severe than first thought after The Bees custodian had surgery last month.
Gottskalksson injured the shoulder towards the end of last season and the operation revealed that up to two-thirds of the shoulder muscle was torn from the bone.
He will be out for up to six weeks while he recovers from the operation and the Scandinavian is set to see the specialist again during that time.
