Change Nginx document root from /usr/share/nginx to /etc/nginx

I've tried many things, STFW, RTFM but I still have this problem. The thing is:

I have a Nnginx installed in an AWS machine (other fella installed it, not me) and I MUST serve several virtual hosts (*.conf files) which are being pulled from other server (production machine)

My main issue, is that the error handlers path in this .conf files are relatives, for example:

html/errores-prxy/handle404.html

as in

 location = /handle404.html {     root html/errores-prxy;}

The problem is that the document root path being called for this handler is /usr/share/nginx, as I can see in the error log:

2015/04/30 10:33:24 [error] 19542#0: *68 open() "/usr/share/nginx/html/errores-prxy/handle404.html" failed (2: No such file or directory), client: 77.240.116.140, server: www.abengoa.com, request: "GET / HTTP/1.1", upstream: "http://172.26.3.9:80/web/", host: "www.abengoa.es"

In this AWS machine, the Nginx is installed in /etc/nginx. And these handler files are in /etc/nginx/html/errores-prxy/handle404.html

So my question would be, how can I make Nginx look in /etc/nginx rather than in /usr/share/nginx/?

I could make a script to change the relative paths to absolute paths in all the *.conf but I'm seeking a more elegant solution as would be changing the Nginx document root.

Many thanks in advance.

Below is my nginx.conf (located in /etc/nginx/nginx.conf, just in case it helps)

user              nginx nginx;worker_processes  2;error_log       /var/log/nginx/error.log;pid             /var/run/nginx.pid;events {                worker_connections  4096;}http {                include         /etc/nginx/conf/mime.types;                default_type    application/octet-stream;                sendfile        on;                gzip            on;                gzip_comp_level 9;                gzip_min_length 0;                gzip_proxied    expired no-cache no-store private auth;                gzip_types      text/plain text/css application/x-javascript application/xml application/javascript;                set_real_ip_from        192.168.151.3;                real_ip_header   X-Forwarded-For;                proxy_set_header   Host             $host;                proxy_set_header   X-Real-IP        $remote_addr;                proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;                proxy_intercept_errors on;                log_format main '$remote_addr - $remote_user [$time_local] ''"$request" $status $body_bytes_sent "$http_referer"''"$http_user_agent"' ;                access_log      /var/log/nginx/access.log main;                client_max_body_size            50m;                client_body_buffer_size         4k;                client_header_buffer_size       2k;                keepalive_timeout               5 5;                client_body_timeout             10;                client_header_timeout           10;                send_timeout                    10;                proxy_connect_timeout           5;                proxy_send_timeout              20;                proxy_read_timeout              120;                proxy_buffer_size               8k;                proxy_buffers                   8 32k;                proxy_busy_buffers_size         32k;                proxy_temp_file_write_size      32k;                server_names_hash_bucket_size   128;                server_names_hash_max_size      1280;                server_name_in_redirect         off;                proxy_cache_path  /etc/nginx/cache  levels=1:2   keys_zone=prxy-cache:100m max_size=256m;                proxy_cache_key   "$scheme$host$request_uri";                include /etc/nginx/conf/*.conf;                include /etc/nginx/conf/sites-enables/*.conf;}