2009 exam roll return question different, explained, question, increase, return

PalacioHill

For Question 8Aiii, the answer states that the increase in convenience yield has the effect of increasing the roll return.  Looking at thismathemetically makes sense: F = Se^(rfr + cost - conv yield)T, so as conv yield goes up, the exponent goes down, and F goes down, making F
However, if you look at this intuitively I think you get a different result.  Roll return is defined (Schweser Book 4 Page 29) as the change in futures price not explained by change in spot price (F-S).  So if convenience yield goes up and forces F down, then F is a smaller number, making F-S a smaller number, and thereby decreasing the roll return.
Am I thinking of this the wrong way?