This 6-arm study will assess the efficacy and safety of RO5024048 (R7128) in combination with the approved doses of Pegasys (180micrograms sc weekly) + Copegus (1000/1200mg po daily) (SOC), versus SOC in treatment-naive patients with chronic hepatitis C, genotype 1 and 4. The first 3 groups will receive 1) RO5024048 500mg bid + Pegasys + Copegus for 12 weeks, followed by SOC for 12 weeks; 2)RO5024048 1000mg bid + Pegasys + Copegus for 8 weeks, followed by SOC for 16 weeks; 3) RO5024048 1000mg bid + Pegasys + Copegus for 12 weeks, followed by SOC for 12 weeks. After 24 weeks, patients in these 3 groups who have achieved rapid viral response will stop treatment, and those who have not will receive SOC for a further 24 weeks. Group 4 will receive RO5024048 1000mg bid + Pegasys + Copegus for 12 weeks, followed by SOC for 36 weeks, and group 5 will receive SOC for 48 weeks. Group 6 provides retreatment on an open-label basis for patients of Group 5 who failed treatment. Patients will receive RO5024048 1000mg bid + Pegasys + Copegus for 24 weeks, followed by SOC for 24 weeks. The anticipated time on study treatment is 6-12 months.