Qeybtaan sii wad - Sanadkii 1846, bilowgii Dagaalkii Mexico iyo Mareykanka, Roberts waxaa dib loogu magacaabay taliye, Mounted Rifles, ee Ciidanka Caadiga ah. Waxaa loo dalacsiiyay kabtan sanadkii 1847, waxaana uu ka qeyb qaatay dagaalkii Veracruz, Cerro Gordo, Contreras, Churubusco
, iyo qabsashada Mexico City, Matamoros iyo Galajara pass. Churubusco, waxaa loo magacaabay major ka dib markii uu hogaamiyay koox hor leh oo weeraryahanno ah. Wuxuu helay shahaado kale, isagoo ahaa kornayl-ku-xigeen 1847 intii lagu jiray dagaalka. Dagaalkii ka dib, wuxuu ka soo shaqeeyay xadka iyo Washington, D.C.