This single-center, randomized, double-blind, two-period crossover study will evaluate the safety, tolerability, pharmacokinetics and pharmacodynamic effects of the combination of multiple doses of RO5285119 with a single dose of risperidone in healthy volunteers. Subjects will be randomized to one of 4 treatment sequences of two periods to receive multiple doses of RO5285119 plus a single dose of risperidone or risperidone placebo or multiple doses of RO5285119 placebo plus a single dose of risperidone or risperidone placebo, with a washout period of approximately 3 weeks between treatment periods. Anticipated time on study is up to 12 weeks (from screening through study completion).