A Study of Obinutuzumab, Polatuzumab Vedotin, and Lenalidomide in Relapsed or Refractory Follicular Lymphoma (FL) and Rituximab in Combination With Polatuzumab Vedotin and Lenalidomide in Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL)

Inclusion Criteria

• Age greater than or equal to (>/=) 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2
• For obinutuzumab in combination with polatuzumab vedotin and lenalidomide (G + Pola + Len) treatment group: R/R FL after treatment with at least one prior chemoimmunotherapy regimen that included an anti-CD20 monoclonal antibody and for which no other more appropriate treatment option exists as determined by the investigator
• For rituximab in combination with polatuzumab vedotin and lenalidomide (R + Pola + Len) treatment group: R/R DLBCL after treatment with at least one prior chemoimmunotherapy regimen that included an anti-CD20 monoclonal antibody in patients who are not eligible for autologous stem-cell transplantation or who have experienced disease progression following treatment with high-dose chemotherapy plus autologous stem-cell transplantation
• Histologically documented CD20-positive B-cell lymphoma as determined by the local laboratory
• fluorodeoxyglucose (FDG)-avid lymphoma (i.e., positron emission tomography (PET)-positive lymphoma)
• At least one bi-dimensionally measurable lesion
• Agreement to remain abstinent or use adequate contraception, among women or men of childbearing potential

Exclusion Criteria

• Grade 3b follicular lymphoma
• History of transformation of indolent disease to diffuse large B-cell lymphoma (DLBCL)
• Known CD20-negative status at relapse or progression
• Central nervous system (CNS) lymphoma or leptomeningeal infiltration
• Prior allogeneic stem-cell transplantation (SCT), or autologous SCT within 100 days prior to Day 1 of Cycle 1
• Current use of systemic immunosuppressant(s), or prior anti-cancer therapy to include: lenalidomide, fludarabine, or alemtuzumab within 12 months; radioimmunoconjugate within 12 weeks; mAb or antibody-drug conjugate within 4 weeks; or radiotherapy/chemotherapy/hormone therapy/targeted small-molecule therapy within 2 weeks prior to Day 1 of Cycle 1
• Active infection
• Positive for human immunodeficiency virus (HIV) or hepatitis B or C
• Receipt of a live virus vaccine within 28 days prior to Day 1 of Cycle 1
• Poor hematologic, renal, or hepatic function
• Pregnant or lactating women
• Life expectancy less than (<) 3 months