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