You can avoid Google doing a barrel roll by encapsulating your query in quotation marks: "do a barrel roll" will not, ironically enough, do a barrel roll.
This should work for all easter egg queries: quotation marks signal to Google that it should search for the literal string instead of interpreting it to mean something else.
This of course doesn't work when Google Instant is turned on, as Google will submit the search query before you can finish encapsulating the query in quotation marks. Unfortunately, this is a limitation/"feature" of Google Instant: to prevent Google from submitting the query before you're finished typing it, you'd have to disable Google Instant.
Beyond this, it's possible to disable certain types of Easter eggs, provided you know the nature of the Easter egg beforehand. You could, for instance, prevent the do a barrel roll Easter egg by adding the following snippet to your browser's custom stylesheet:
But since this would affect every
<body> tag on every webpage, it's not ideal either.
You could get around this by using Stylish, which allows you to specify site-specific custom stylesheets ("userstyles"). Creating a userstyle with the following should work: