Milwaukee netted a fourth outfielder, Gerardo Parra, while the defending National League champions added two starting pitchers who will face the Brewers this weekend. Roenicke plans to get Parra, who did not start Friday night, into the lineup this weekend.
Roenicke said general manager Doug Melvin tried for other deals but the asking price was too high.
New Cardinals starters Justin Masterson and John Lackey will pitch for St. Louis on Saturday and Sunday. The Brewers altered their rotation, too, moving up Kyle Lohse (11-5, 3.07) and Matt Garza (7-7, 3.74) a day each for the last two games of the series.
Jimmy Nelson (1-2, 4.30) had been listed as the starter Saturday and was scratched due to a blister.
''With St. Louis, it was a great pickup for those two guys,'' Roenicke said. ''Saying that, I know Doug was on the phone making calls and I know what people were asking for in return, and for me it didn't make sense.
''It's nice when you can have a player finish up the year with you and help you win, but then what do you do next year if you give away some guys you're counting on?''
Roenicke said he told Khris Davis he was still the left fielder, and Davis started Friday night. The manager had slotted Parra for a favorable matchup Sunday against Lance Lynn before the Cardinals subbed in Lackey for the series finale.
''People they were asking for, it was just too much,'' Roenicke said.
Parra was batting .259 with six homers, 30 RBIs and five steals in 104 games with the Diamondbacks. He replaces Logan Schafer, who was optioned to the minors.
''He's a nice addition,'' Roenicke said. ''When he spells a guy, we're still good.''
Scooter Gennett was scratched from the lineup Friday with a bruised left index finger sustained bunting in early batting practice and was day to day.
''He finished hitting and was sore,'' Roenicke said. ''I'm hoping he just pinched it.''
Elian Herrera replaced Gennett at second base and batted eighth against the Cardinals on Friday night.
Gennett had been batting fifth in the original lineup. The players batting behind him - Davis, Lyle Overbay and Jean Segura - all moved up one spot.
Gennett was hitting .302 with eight homers and 35 RBIs. Herrera was hitting .270 in 89 at-bats with two RBIs.
Reliever Jim Henderson, sidelined with shoulder inflammation, completed a rehab stint and told the team he didn't feel ready to be activated. Henderson will return to Arizona and try to strengthen the arm.
Roenicke said the velocity was down and Henderson, who's on the 60-day disabled list, wouldn't have been available to pitch three straight days. Henderson is 2-1 with a 7.15 ERA in 14 games and hasn't pitched since May 1.
''It's not that he's hurting,'' Roenicke said. ''It's just that he can't get back to where he feels like he's ready.''