1 sn Paul does not mean here that he is going to bestow upon the Roman believers what is commonly known as a “spiritual gift,” that is, a special enabling for service given to believers by the Holy Spirit. Instead, this is either a metonymy of cause for effect (Paul will use his own spiritual gifts to edify the Romans), or it simply means something akin to a blessing or benefit in the spiritual realm. It is possible that Paul uses this phrase to connote specifically the broader purpose of his letter, which is for the Romans to understand his gospel, but this seems less likely.
2 tn A figurative extension of ὀψώνιον (oywnion), which refers to a soldier’s pay or wages. Here it refers to the end result of an activity, seen as something one receives back in return. In this case the activity is sin, and the translation “payoff” captures this thought. See also L&N 89.42.