Since it uses LWP under it, you can customized it very easily.
The only thing that I missed was a Pod description about setting SSL options with it, but this is probably something to be checked in LWP itself. Anyway, I believe this usage is common enough to have a specific method to disable certificate checking. I solved it by doing a simple:
my $client = REST::Client->new();
$client->getUseragent()->ssl_opts( verify_hostname => 0 );
But as I said, I had to go through LWP::UserAgent to get that and well... there are a lot of options to set SSL/TLS with new() parameters, adding another one would do no harm.