A.T. Robertson Commentary Romans 15:27

"Yea, it hath been their good pleasure; and their debtors they are. For if the Gentiles have been made partakers of their spiritual things, they owe it [to them] also to minister unto them in carnal things." — Romans 15:27 (ASV)

Their debtors (οφειλετα αυτων). Objective genitive: the Gentiles are debtors to the Jews. See the word οφειλετης in 1:14; 8:12.

For if (ε γαρ). Condition of the first class, assumed as true, first aorist active indicative (εκοινωνησαν, from κοινωνεω, to share) with associative instrumental case (πνευματικοις, spiritual things).

To minister unto (λειτουργησα, first aorist active infinitive of λειτουργεω with dative case αυτοις, to them), but here certainly with no "sacerdotal" functions (cf. verse 16).

In carnal things (εν τοις σαρκικοις). Things which belong to the natural life of the flesh (σαρξ), not the sinful aspects of the flesh at all.