A common assumption is that a lighter roast, like Starbucks' Blonde, has less caffeine than a darker one, like Pike Place. Starbucks' own published data doesn't back that up here: a Grande (16 fl oz) Starbucks Pike Place Roast is listed at 315-390 mg, and the same size Starbucks Blonde Roast (Sunsera) is listed at the identical 315-390 mg.

Roast level changes flavor more than it changes caffeine; brew method, bean dose and steep time matter more. See the source link in the table below, or add either one to the caffeine calculator to see how it fits your personal daily limit.

Grande, side by side

Starbucks Pike Place Roast, Grande, 16 fl oz (473 ml) 315-390 mg
Starbucks Blonde Roast (Sunsera), Grande, 16 fl oz (473 ml) 315-390 mg

Sources

Drink Serving Caffeine Source
Starbucks Pike Place Roast Grande, 16 fl oz (473 ml) 315-390 mg Starbucks published nutritionSource
Starbucks Blonde Roast (Sunsera) Grande, 16 fl oz (473 ml) 315-390 mg Starbucks published nutritionSource

Only the Grande size of each roast is shown above; see each drink's own page for Short, Tall and Venti figures.