I'll tell you what...
You show us where the word *fast* is in Romans 14 to show that Paul was actually talking about fasting like you claim.
Not exactly the word ‘fast’ but it does allude to the days one eats and the days one does not. I'll refer back to King Jimmy for this one.
Rom 14:5 One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind. 6 He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it. He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.
Verse 6 directs us back to verse 5 for context about the ones eating and the ones that are not eating as to say, ones that are fasting as that is what fasting is, not eating. Knowledge of the practices and customs, aka traditions on fasting, is of great help in order to discern the language and idioms of the day and times in which they were written. We can not presume to think that they thought and spoke just as we do but one thing is for sure, the customs and traditions for fasting have not changed and still remain the same to this day and they are different for every branch whether Jew or Greek therfore we are to respect each others difference in regards to eating and not eating whether it be in fasting or in the matter of meat offered to false gods such as still done in many religions.