Contradiction with Matthew 7:14
This verse suggests that only a few find eternal life, contrasting with Romans 9:27's statement on the large number of the children of Israel.
Matthew 7:14: Because strait [is] the gate, and narrow [is] the way, which leadeth unto life, and few there be that find it. [Because: or, How]
Contradiction with Romans 11:26
This verse states that all Israel will be saved, contradicting Romans 9:27 which implies only a remnant will be saved.
Romans 11:26: And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
Contradiction with Isaiah 10:22
This verse, which Paul quotes in Romans 9:27, suggests that only a remnant will return, yet elsewhere in the Bible, the promise of widespread restoration is made.
Isaiah 10:22: For though thy people Israel be as the sand of the sea, [yet] a remnant of them shall return: the consumption decreed shall overflow with righteousness. [of them: Heb. in, or, among, etc] [with: or, in]
Contradiction with John 3:16
This verse promises salvation to "whosoever believeth," contrasting with the limited scope suggested in Romans 9:27.
John 3:16: For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.