While the US CDC does recommend avoiding sharing of personal items that could potentially have blood on them like razors, fingernail clippers and yes tooth brushes that is considered to be a small risk and the possibility of brushes touching would be that much even smaller.
Also bear in mind in order to transmit hepatitis c there must be blood that has hepatitis c on the brush and that blood would have to enter the blood stream of an uninfected person. So one of your roommates would need to be infected with hepatitis c and bleed on their brush not rinse the brush have enough blood get on your brush and then that blood would have to enter your blood stream. Not a very likely scenario.
Hep c is difficult to contract. Most cases are due to the sharing of IV drug injection needles with other drug users or having a blood transfusion before 1990 when antibody testing for hep c was developed and the blood supply secured.
Even in the case of a health care worker who should experience an accidental needle stick involving a patient with known hep c the odds of transmission are only about 1.8%