A Study Evaluating Safety and Efficacy of Obinutuzumab, Polatuzumab Vedotin (Pola), and Atezolizumab (Atezo) in Participants With Relapsed or Refractory Follicular Lymphoma (FL) and Rituximab, Atezo, and Pola in Participants With Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL)

Inclusion Criteria:

- Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1, or 2

- For obinutuzumab + Atezo + Pola treatment group: relapsed or refractory FL after
treatment with at least one prior chemoimmunotherapy regimen that included an
anti-Cluster of Differentiation (CD)20 monoclonal antibody and for which no other more
appropriate treatment option exists as determined by the investigator

- For rituximab + Atezo + Pola treatment group: relapsed or refractory DLBCL after
treatment with at least one prior chemoimmunotherapy regimen that included an
anti-CD20 monoclonal antibody, in participants who are not eligible for second line
combination (immuno-) chemotherapy and autologous stem-cell transplantation or who
have failed second line combination (immuno-) chemotherapy or experienced disease
progression following autologous stem-cell transplantation

- Histologically documented CD20-positive lymphoma and fluorodeoxyglucose (FDG)-avid
lymphoma (that is PET-positive lymphoma) with at least one bi-dimensionally measurable
lesion

- Availability of a representative tumor specimen and the corresponding pathology report
for retrospective central confirmation of the diagnosis of FL or DLBCL

- For women who are not postmenopausal or surgically sterile: agreement to remain
abstinent or to use contraceptive methods that result in a failure rate of less than
(<) 1% per year during the treatment period for greater than or equal to (>=) 5 months
after last dose of Atezo, >= 12 months after last dose of rituximab, >= 12 months
after last dose of Pola, and >= 18 months after last dose of obinutuzumab

- For men: agreement to remain abstinent or to use contraceptive measures that result in
a failure rate of <1% per year during the treatment period and for at least 3 months
after last dose of obinutuzumab, rituximab, and Atezo and for 5 months after last dose
of Pola, and agreement to refrain from donating sperm during this same period

Exclusion Criteria:

- Grade 3b follicular lymphoma

- History of transformation of indolent disease to DLBCL

- Known CD20-negative status at relapse or progression; CNS lymphoma or leptomeningeal
infiltration

- Prior allogeneic stem cell transplantation (SCT), completion of autologous SCT within
100 days prior to Day 1 of Cycle 1 (D1C1)

- Prior anti-cancer therapy including: Fludarabine or alemtuzumab within 12 months prior
to D1C1; radioimmunoconjugate within 12 weeks prior to D1C1; monoclonal antibody or
antibody drug conjugate (ADC) within 5 half-lives or 4 weeks prior to D1C1 ;
radiotherapy, chemotherapy, hormonal therapy, or targeted small-molecule therapy
within 2 weeks prior to D1C1; anti-programmed death-1 (anti-PD-1), anti-programmed
death-ligand 1 (anti-PD-L1), anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA4),
anti-CD137/41-BB agonist, or anti-CD40 agonist antibodies

- Treatment with systemic immunosuppressive medications, including but not limited to
prednisone, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor
agents within 2 weeks prior to D1C1

- History of solid organ transplantation and of severe allergic or anaphylactic reaction
to humanized, chimeric, or murine monoclonal antibodies

- Active infection; positive for hepatitis B surface agent (HbsAg), total hepatitis B
core antibody (HBcAb), or hepatitis C virus (HCV) antibody at screening; known history
of HIV positive status, progressive multifocal leukoencephalopathy (PML), autoimmune
disease

- Vaccination with a live virus vaccine or live attenuated vaccine within 28 days prior
to D1C1

- Pre-existing Grade greater than (>) 1 neuropathy

- Major surgical procedure other than for diagnosis within 28 days prior to D1C1

- Inadequate hematologic function, renal function, and liver function

- Pregnant or lactating women

- Life expectancy < 3 months