Displaying the results of an RNG as a player message, not an announcement

Hello all! 

I hope this is the right place to post this (I'm brand new to this site, so I wasn't entirely sure..)
I've been working on creating a custom dice rolling mod for a server I help run. The Idea is that a player will be able to enter in a command (Such as /roll 4d20+5) or some variation of it, and have the results be displayed in chat as if said by the player, rather than being announced to the entire server. This way groups of players can get together and use the rolling command to share results with each other, and the chat won't be filled with every player's roll from across the server. 

However, I'm having trouble getting this to work. Using the Execute command with /say doesn't seem to be working. 

I'll attach a picture of the most basic build for the mod, where I'm just trying to get the results display working. 

Any help is appreciated! And keep in mind, I'm a coding novice ^^'