Well if this was aimed at the Jews then yes.
Luk 18:11 The Pharisee stood and prayed thus with himself, 'God, I thank You that I am not like other menâextortioners, unjust, adulterers, or even as this tax collector.
Luk 18:12 I fast twice a week; I give tithes of all that I possess
There's nothing in scripture that mandates fasting twice a week but among the pharisee's it was apparently a test of piety. So Romans 14 could be referring to this. In addition it could be referring to purchasing meat in the meat market that had been sacrificed to idols...a concern in the early Christian church. The "days" referred to might have been the days that meat was sacrificed to idols and put out in the meat markets to be sold afterwards.
A lot of ‘coulds’ in your statement.