You have to see https://github.com/adnanademovic/rosrust/tree/master/examples instead of this.
Tutorial code of rosrust.
$ cargo build
$ roscore
$ cargo run --bin publisher
or,
$ ./target/debug/publisher
$ cargo run --bin subscriber
or
$ ./target/debug/subscriber
Add more message to build.rs.
#[macro_use]
extern crate rosrust;
rosmsg_main!("std_msgs/String", "more_msgs/SomeMsg");
then, you can use msg::more_msgs::SomeMsg in the sample code.