This randomized, double blind, phase II study will evaluate the efficacy and safety of two doses of RO5024048 in combination with ritonavir-boosted danoprevir and Pegasys (peginterferon alpha-2a) and Copegus (ribavirin) in patients who failed a prior protease inhibitor containing regimen with or without pegylated interferon. Patients will be randomized to receive either a 2-week lead-in of RO5024048 (1500 mg or 1000 mg orally twice daily) in combination with Pegasys (180 mcg subcutaneously weekly) and Copegus (1000 mg or 1200 mg orally daily) followed by 24 weeks of therapy with RO5024048 in combination with danoprevir (100 mg orally twice daily) plus ritonavir (100 mg orally twice daily) and Pegasys and Copegus (QUAD therapy), or 24 weeks of therapy with RO5024048 in combination with danoprevir plus ritonavir and Pegasys and Copegus (QUAD therapy). Anticipated time on study treatment is 24 or 26 weeks, with a treatment-free follow-up of 24 weeks.

Inclusion Criteria:

• Adult patients, >/= 18 years of age
• Hepatitis C genotype 1 infection
• Serum HCV quantifiable by Roche COBAS TaqMan HCV Test v2.0
• Liver biopsy (within 24 months) or Fibroscan (within 12 months) before first administration of study drug consistent with chronic hepatitis C and demonstrating absence of liver cirrhosis
• Documented failed prior treatment with protease inhibitor (evidenced by viral breakthrough or partial response while on treatment or relapse after treatment), including documentation on treatment with other direct-acting antiviral agents and other HCV antiviral treatment
• Patients must have discontinued prior HCV treatment at least 24 weeks prior to first dose of study drug in this trial

Exclusion Criteria:

• Infection with any HCV genotype other than genotype 1
• Evidence of any variants associated with protease inhibitor resistance at screening
• Body mass index (BMI) <18 or >/=36 kg/m2
• Positive for hepatitis A or hepatitis B infection
• Use of any systemic antiviral therapy with perceived activity against HCV \