Looking further into it I believe there is something missing from the nginx.conf causing improper responses:
Remote Address:example.com:80
Request URL:http://example.com/wp-admin/admin-ajax.php?action=roksprocket&nonce=4e79d82c02
Request Method:POST
Status Code:200 OK
Request Headers
Accept:text/javascript, text/html, application/xml, text/xml, */*
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8,es;q=0.6
Connection:keep-alive
Content-Length:158
Content-type:application/x-www-form-urlencoded; charset=UTF-8
Cookie:wordpress_8d5c55f263f1fbeaeacab59de0ed539f=webmaster%7C1399299571%7Cc45cc66c20278417596ac7a86a44f14c; gantry-android-switcher=1; PHPSESSID=lc8g3abuip5geje0mfq9c2m0v2; wp-settings-time-1=1399126752; wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_8d5c55f263f1fbeaeacab59de0ed539f=webmaster%7C1399299571%7C9762057a27f2113db6f91e2435df4d87; roksprocket-showitems=1; gantry-android-switcher=1; wp-settings-time-3=1399174698
Host:example.com
Origin:http://example.com
Referer:http://example.com/wp-admin/admin.php?page=roksprocket-edit&nonce=4e79d82c02&paged=1&id=0
User-Agent:Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/34.0.1847.131 Safari/537.36
X-Requested-With:XMLHttpRequest
Query String Parameters
action:roksprocket
nonce:4e79d82c02
Form Data
id:0
uuid:eb62825b-8b2c-4251-cd0b-ddcfabf45c5c
title:test
params[provider]:wordpress
params[layout]:tabs
task:
model:edit
model_action:save
model_encoding:form
Response Headers
Access-Control-Allow-Credentials:true
Access-Control-Allow-Headers:Content-Type, Authorization, X-Requested-With
Access-Control-Allow-Methods:GET, PUT, POST, DELETE, OPTIONS
Access-Control-Allow-Origin:localhost
Access-Control-Allow-Origin:http://example.com
Cache-Control:no-cache, must-revalidate, max-age=0
Content-Encoding:gzip
Content-Type:text/html; charset=UTF-8
Date:Sun, 04 May 2014 03:38:37 GMT
Expires:Wed, 11 Jan 1984 05:00:00 GMT
Pragma:no-cache
Server:nginx
Transfer-Encoding:chunked
Vary:Accept-Encoding
X-Content-Type-Options:nosniff
X-Frame-Options:SAMEORIGIN
X-Robots-Tag:noindex