Inclusion Criteria:

          -  Men and women 18 years of age or older.

          -  Pathologically proven diffuse large B-cell lymphoma.

          -  No prior systemic therapy for lymphoma.

          -  NCCN-IPI risk score of 2 or higher.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.

          -  Life expectancy of ≥3 months.

          -  Ann Arbor stage II-IV

          -  Measurable disease, meaning at least 1 lymph node or other lymphomatous lesion with a
             long axis of ≥1.5 cm by CT imaging, and at least one FDG-avid lesion by FDG-PET scan.

          -  Left ventricular ejection fraction of at least 45% by either echocardiography or
             radionucleotide angiography.

          -  Ability to swallow oral tablets without difficulty.

          -  All subjects with preserved reproductive potential must agree to practice abstinence
             or employ contraceptive measures for the duration of treatment and for 4 weeks
             following final dosing. All male subjects are considered to have reproductive
             potential. Female subjects of reproductive potential are those who: 1) are not at
             least 50 years old and have no menses for 24 consecutive months; or 2) have not been
             rendered surgically sterile (having undergone hysterectomy and/or bilateral
             salpingo-oophorectomy). Female subjects of reproductive potential must have a negative
             serum pregnancy test (minimum sensitivity 25 IU/L or equivalent units of human
             chorionic gonadotropin ([hCG]) within 7 days of first day of drug dosing.

          -  Meet the following clinical laboratory requirements: - Creatinine clearance ≥30 ml/min
             by Cockcroft-Gault formula ; - Total bilirubin ≤ 1.5 × upper limit of normal (ULN)
             (unless indirect bilirubin is elevated due to Gilbert's syndrome or hemolysis); - AST
             and ALT≤ 3 × ULN; - Platelet count ≥ 50,000/μL, with or without transfusion support; -
             ANC ≥ 1000/μL, with or without chronic granulocyte growth factor support; - Hemoglobin
             ≥8 g/dL, with or without transfusion support.

        Exclusion Criteria:

          -  Allergy or intolerance to roflumilast.

          -  Any active malignancy other than DLBCL

          -  Prior allogeneic bone marrow transplant within 12 months of screening date.

          -  Prior autologous stem cell transplant within 6 months of screening date.

          -  Immunotherapy, chemotherapy, radiotherapy, or investigational therapy within 6 months
             prior to drug dosing.

          -  Active central nervous system (CNS) involvement by lymphoma, including untreated
             symptomatic epidural disease

          -  Active uncontrolled infection.

          -  Clinically documented history of severe depression and/or suicidal thoughts or
             behavior.

          -  Uncontrolled illness including but not limited to: symptomatic congestive heart
             failure (New York Heart Association [NYHA] Class III or IV heart failure), unstable
             angina pectoris, uncontrolled cardiac arrhythmia, and psychiatric illness that would
             limit compliance with study requirements.

          -  History of myocardial infarction, acute coronary syndromes (including unstable
             angina), coronary angioplasty and/or stent placement within 6 months prior to study
             drug dosing.

          -  History of another active cancer within 2 years prior to study drug dosing, excluding
             adequately treated basal cell or squamous cell carcinoma of the skin, cervical cancer
             in situ, or other adequately treated in situ carcinoma.

          -  History of major surgery within 3 weeks or minor surgery within 1 week of roflumilast
             administration. Major surgery includes, for example, any open or laparoscopic entry
             into a body cavity, or operative repair of fracture; minor surgery includes, for
             example, open surgical biopsy of palpable/superficial lymph node, or placement of
             vascular access device.

          -  Other medical or psychiatric illness or organ dysfunction, which in the opinion of the
             investigator, would either compromise the subject's safety or interfere with the
             evaluation of the safety of the study agent.

          -  Corrected QT interval (QTc) prolongation (defined as a QTc >450 ms for males and >470
             ms for females [Fridericia's correction]) or other clinically significant ECG
             abnormalities as assessed by the investigator.

          -  Patients known to be HIV-positive must not have multi-drug resistant HIV infection,
             CD4 counts < 150/μl or other concurrent AIDS-defining conditions. Serologic screening
             for HIV is required within the 6 months prior to study enrollment.

          -  Patients positive for Hepatitis B surface antigen (HBsAg) or Hepatitis C-virus
             ribonucleic acid (HCV RNA), unless both AST and ALT≤1.25 x ULN and there is no known
             history of chronic active hepatitis. Serologic screening for hepatitis B and C testing
             is required within the 6 months prior to study enrollment.

          -  Patients with moderate or severe liver impairment, as defined by a Child-Pugh class of
             B or C.

          -  Women who are pregnant or breastfeeding.

          -  Current use of any of the following medications: boceprevir, carbamazepine,
             ciprofloxacin, cobicistat, conivaptan, enzalutamide, fluvoxamine, itraconazole,
             ketoconazole, mitotane, phenytoin, posaconazole, rifampin, ritonavir, St. John's Wort,
             telaprevir, voriconazole, or zafirlukast.

          -  Current use of non-nucleoside reverse transcriptase inhibitors (NNRTI) including
             efavirenz, rilpivirine, etravirine, delavirdine, nevirapine, and lersivirine.