Kammala jumla mai zuwa: A 1861, a lokacin da yake da shekaru 19, Roberts ya shiga aikin soja a Kamfanin C na 19th Regiment North Carolina Infantry, wanda daga bisani za a sanya shi a matsayin 2nd Regiment NC Cavalry. Bayan da ya yi aiki tare da bambanci a lokacin ayyukan regimental a Arewacin Carolina, amma ba tare da horar da sojoji ba, an ci gaba da shi zuwa na biyu a ranar 30 ga Agusta, 1861. Ranar 13 ga Satumba, 1862, an ba da Roberts ga Firayim Minista. An tura rukunin Roberts zuwa Virginia a cikin kaka na wannan shekarar kuma ya shiga cikin yaƙe-yaƙe da yawa, daga cikinsu: Yaƙin Fredericksburg, Yaƙin Suffolk, da Yaƙin Brandy Station. Ranar 13 ga watan Nuwamba, 1863, Roberts ya ci gaba da zama kyaftin din kuma daga bisani ya zama babban jami'in kafin bazara na 1864, lokacin da ya yi yaƙi a brigade na Arewacin Carolina na William Henry Fitzhugh Lee. An daukaka shi zuwa colonel a watan Yunin 1864 kuma a lokacin Siege na Petersburg, an ba shi umurnin 2nd Regiment NC Cavalry. Roberts ya jagoranci cajin da aka yi wa Union breastworks, ya sauka, ya wuce ramukan bindigogi kuma ya kama wasu sojoji na Tarayyar Turai a
Yaƙin na biyu na tashar Ream a ranar 25 ga Agusta, 1864. Ranar 23 ga Fabrairu, 1865, Roberts ya ci gaba da zama brigadier janar. Bisa ga al'ada, Janar Robert E. Lee ya gabatar da Roberts tare da gauntlets na sirri na Lee a matsayin godiya ga aikin da Roberts ya yi. Roberts ya ci gaba da umurnin brigade a yakin Five Forks, kuma daga bisani ya mika wuya a yakin Appomattox Court House, a ranar 9 ga Afrilu, 1865.