Anthony/Doug, funny enough we actually had that exact use case for our designers at one point.
Megan - this was the value expression we used, which is identical to Anthony's formula + Doug's suggestion, except instead of nesting in another IF statement, we added in an "and" condition (syntax is just "&&"). I try to use "and" (&&) and "or" (||) conditions whenever possible instead of nested IF statements because they (usually) help keep the formula shorter and easier to read (plus less chance of missing a closed parenthesis). Just putting this all out here in case someone else needs it in the future.
valueexpression=IF({numberOfChildren}>0,"",IF(ISBLANK({handoffDate}),"",IF(ISBLANK({actualCompletionDate})&&{roleID}=YOURROLEIDHERE,{name},"")))
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You can also use Role Name by switching {roleID} with {role}.{name} and put the name in parentheses where YOURROLEIDHERE is in the formula. So if your role was "Designer", it would look like {role}.{name}="Designer"
Not sure how it would handle a task that is assigned to someone with a secondary role of "Designer" though. I think Role ID only reads the primary role.