Both pitchers were available for Wednesday night's game against the Arizona Diamondbacks.
Brown is making his third appearance on Colorado's roster. He last pitched for the Rockies on June 16 before going on the 15-day disabled list two days later with right shoulder inflammation.
He was activated Aug. 22 and optioned to Albuquerque. Brown is 0-2 with a 3.86 ERA in 24 games for Colorado.
Miller, who was optioned Aug. 23, is in his fourth stint with the Rockies. He is 1-2 with 4.58 ERA in 19 appearances for Colorado.