This study is testing a new combination of drugs (glofitamab, gemcitabine, and oxaliplatin) for treating **relapsed or refractory diffuse large B-cell lymphoma (DLBCL)**, a type of blood cancer that either returned after treatment or didn't respond to initial treatment. The study aims to include diverse participants in the U.S. **Eligibility**: Participants must have DLBCL that has either returned after at least six months or not responded to previous treatment. They should have received at least one prior treatment and have measurable tumors. They should not have been treated with certain drugs before or have specific health conditions. **Exclusions**: Those who participated in a related study, have certain genetic conditions, or have other serious health issues like severe allergies, autoimmune diseases, or recent infections cannot join. **Key Points**: - **Study Duration**: Participation involves multiple visits for treatment and monitoring. - **Compensation**: Participants may receive compensation for their time and travel. - **Risks**: As with all clinical trials, there may be side effects or risks associated with the treatment. Please consult with a healthcare professional to understand if joining this study is a good choice for you.