As he walked up and down the row, he shouted 'Hot dogs! Get your hot dogs!'
Literal
Row [object-を] up [at-に] down [at-に] walk-around time, 'hot-dog [how-about-いかが]? Hot-dog [how-about-いかが]?' [quotative-と] shouts.
A vendor scene at a stadium or event. 歩き回る ('walk around, wander') + 時 ('when') as a subordinate clause frame. The vendor's cry is marked as direct speech with 「...」 and the quotative と. いかが ('how about, would you like') is a polite form of どう. 叫ぶ ('to shout, cry out') in plain non-past works as generic present — 'he shouts' (customary/habitual).