EDIT AFTER COMMENT
Please see the fiddle for an inline form in a Jumbotron with the button in-line (not below centered), and fieldset.
Note : that I changed the vertical alignment of the checkbox and radio + add some right margin, and an extra small button. The form will go as block if the screen is extra-small as a bootstrap behavior.
<div class="jumbotron">
<form class="form-inline">
<fieldset class="radiogroup">
<legend>Sorting Criteria</legend>
<label for="id_price_order_0">
price order
<span class="asteriskField">*</span>
</label>
<label class="radio" for="id_price_order_1">
lowest
<input type="radio" checked="checked" id="id_price_order_1" />
</label>
<label class="radio" for="id_price_order_2">
highest
<input type="radio" id="id_price_order_2" />
</label>
<label for="id_newest_entry" class="requiredField checkbox">
latest date
<input id="id_newest_entry" type="checkbox" />
</label>
<label for="id_latest_year" class="requiredField checkbox">
latest year
<input id="id_latest_year" type="checkbox" />
</label>
<input type="submit" name="submit" value="Submit" class="btn btn-primary btn-xs" />
</fieldset>
</form>