Bootstrap has native support for keyboard navigation.
Just add role="menu" to your dropdown-menu
Here is an example, just save as .html and take a test
<html>
<head>
<link href="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" rel="stylesheet">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="btn-group">
<button class="btn btn-default">1</button>
<button class="btn btn-default">2</button>
<button class="btn btn-default">3</button>
<div class="btn-group">
<button class="btn btn-default dropdown-toggle" data-toggle="dropdown">menu</button>
<ul class="dropdown-menu" role="menu">
<li> <a href="#">one</a> </li>
<li> <a href="#">two</a> </li>
<li> <a href="#">three</a> </li>
</ul>
</div>
</div>
</body>
</html>
http://jsfiddle.net/damphat/WJS9p/