Two studies were conducted to evaluate the inclusion of additional roughage in wheat-based diets containing modified distillers’ grains with solubles on feedlot performance (Study 1) and digestibility, ruminal pH, and ruminal fermentation characteristics (Study 2). Study 1 used 72 steers (391.6 ± 46.3 kg) and study 2 used 4 ruminally and duodenally cannulated steers (393.4 ± 33.0 kg). Feedlot performance and carcass characteristics, excluding marbling, were not affected by increasing roughage (P ≥ 0.20). Ruminal pH increased linearly (P < 0.01) as rate of roughage inclusion increased. Concentrations of acetate and butyrate increased, and propionate decreased in a linear fashion (P < 0.01), increasing acetate and butyrate to propionate ratio (P < 0.01) with increasing dietary roughage. Our data indicate that increasing roughage inclusion in wheat-based diets including modified distillers’ grains with solubles increased ruminal pH and shifted ruminal fermentation patterns without affecting feedlot performance.