A Study of Decreased Dose Frequency in Participants With Systemic Juvenile Arthritis Who Experience Laboratory Abnormalities During Treatment With RoActemra/Actemra (Tocilizumab)

Inclusion Criteria: PART 1 and 2 * Children 2 to 17 years of age inclusive at screening * Systemic juvenile idiopathic arthritis (sJIA) according to International League of Associations for Rheumatology (ILAR) classification (2001) and sJIA symptoms lasting for at least 1 month since diagnosis of sJIA * Must meet one of the following: * Not receiving methotrexate (MTX) or discontinued MTX at least 4 weeks prior to baseline visit, or * Taking MTX for at least 12 weeks immediately prior to the baseline visit and on a stable dose of less than or equals (\</=) 20 milligrams per meter square (mg/m\^2) for at least 8 weeks prior to the baseline visit, together with either folic acid or folinic acid according to local standard of care * Participants entering Part 1 who are naive to TCZ therapy must also meet the following inclusion criterion: * History of inadequate clinical response (in the opinion of the treating physician) to Non steroidal Anti-Inflammatory Drugs (NSAIDs) and corticosteroids PART 2 * Juvenile Arthritis Disease Activity Score (JADAS) -71 score of 3.8 or less and absence of fever (related to sJIA) at screening and baseline * Neutropenia, thrombocytopenia, or elevated Alanine transaminase/Aspartate transaminase (ALT/AST) previously experienced on the labeled dose (Q2W) of RoActemra/Actemra at any time * Not currently receiving oral corticosteroids, or taking oral corticosteroids at a stable dose for a minimum of 2 weeks prior to baseline visit at no more than 10 milligrams per day (mg/day) or 0.2 miiligrams per kilogram per day (mg/kg/day), whichever is less * Not taking (NSAIDs), or taking no more than 1 type of NSAID at a stable dose for a minimum of 2 weeks prior to the baseline visit, with the dose being less than or equal to the maximum recommended daily dose Exclusion Criteria: * Wheelchair bound or bedridden * Any other auto-immune, rheumatic disease, or overlap syndrome other than sJIA * Pregnant or lactating, or intending to become pregnant during study conduct and up to 6 months after the last administration of study drug * Any significant concurrent medical or surgical condition which would jeopardize the participant's safety or ability to complete the trial * History of significant allergic or infusion reactions to prior TCZ infusion, and/or presence of anti-TCZ antibodies at screening * Inborn conditions characterized by a compromised immune system * Known Human Immunodeficiency Virus (HIV) infection or other acquired forms of immune compromise * History of alcohol, drug, or chemical abuse within 6 months of screening * Evidence of serious uncontrolled concomitant diseases, including but not limited to the nervous, renal, hepatic, or endocrine systems * Any active acute, subacute, chronic or recurrent bacterial, viral, or systemic fungal infection * History of atypical tuberculosis (TB) * Active TB requiring treatment within 2 years prior to the screening visit * Positive purified protein derivative (PPD) at screening * Any major episode of infection requiring hospitalization or treatment during screening or treatment with IV antibiotics completing within 4 weeks of the screening visit or oral antibiotics completing within 2 weeks of the screening visit * History of reactivation or new onset of a systemic infection within 2 months of the screening visit * Positive for hepatitis B or hepatitis C infection * Chronic hepatitis, viral or pulmonary disease * Significant cardiac or pulmonary disease * History of or current cancer or lymphoma * Uncontrolled diabetes mellitus * History of or concurrent serious gastrointestinal disorders * History of macrophage activation syndrome (MAS) within 3 months prior to screening visit