Hmmm, looking it up, 5150 went to number 2 on the billboard album charts, while Eat 'Em and Smile peaked at number 4, and the biggest hit from 5150, Why Can't This Be Love?, went to number 3 on the top 40 charts, while Yankee Rose was Roth's biggest hit from his album, peaking at number 16.
Regardless, I think Roth and Van Hagar both did pretty damn well in the mid to late 80s. I remember the day after Roth was here on the Skyscraper tour in '88, I was in high school, and I saw a ton of kids wearing concert t-shirts from that show the next day at school.