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)

All participants will receive lenalidomide oral capsules at doses of 10, 15, or 20 milligrams (mg) on Days 1 to 21 of each 28-day cycle for up to 6 Cycles in dose escalation phase followed by post-induction treatment at a dose of 10 mg once daily on Days 1 to 21 of each subsequent 28-day cycle. Post-induction lenalidomide may continue for up to 12 months until disease progression or unacceptable toxicity for participants with R/R FL and up to 6 months until disease progression or unacceptable toxicity for participants with R/R DLBCL.

Participants will receive a fixed dose of obinutuzumab, 1000 mg via intravenous (IV) infusion to be given on Days 1, 8 and 15 of Cycle 1 and on Day 1 of Cycles 2 to 6 followed by post-induction treatment at a dose of 1000 mg via IV infusion on Day 1 of every other month for up to 24 months until disease progression or unacceptable toxicity.

Participants with R/R FL will receive polatuzumab vedotin via IV infusion at doses of 1.4 or 1.8 milligrams per kilogram (mg/kg) on Day 1 of each 28-day cycle for up to 6 months during induction treatment. Participants wit R/R DLBCL will receive polatuzumab vedotin via IV infusion at dose 1.8 mg/kg on Day 1 of each 28-day cycle for up to 6 months during induction treatment.

Participants will receive a fixed dose of rituximab, 375 mg/m\^2 via intravenous (IV) infusion to be given on Days 1 of Cycle 1 to 6 followed by post-induction treatment at a dose of 375 mg/m\^2 via IV infusion on Day 1 of every other month for up to 6 months, until disease progression or unacceptable toxicity.