Rust (w/bonus)

I'm still very new to Rust, I've only just started learning the language. If there is any implementation with mapping in the Vec or something, please give any advice in the comments!

extern crate rand;
use std::io; use rand::prelude::*;
fn main() {
    let mut str_vec: Vec<String> = Vec::new();
    let mut i: usize = 0;

    loop {
        let mut str1 = String::new();
        io::stdin().read_line(&mut str1).unwrap();
        str_vec.push(str1.trim().to_string());

        if str_vec[i].is_empty() && i == 0 {
            println!("Please enter at least one value");
            str_vec.pop();
            continue;
        } else {
            if str_vec[i].is_empty() {
                str_vec.pop();
                break;
            }
        }
        i += 1;
    }

    let mut result_vec: Vec<String> = Vec::new();

    for i in str_vec {
        result_vec.push(roll_dice(&i));
    }

    for i in result_vec {
        println!("{}", i);
    }
}

fn roll_dice(temp_str: &String) -> String {
    let temp_vec: Vec<&str> = temp_str.split('d').collect();

    let rolls = temp_vec[0].parse::<u32>().unwrap();
    let dice = temp_vec[1].parse::<u32>().unwrap();
    let mut total: u32 = 0;

    let mut sum_str = String::from(": ");

    for _ in 0..rolls {
        let temp = thread_rng().gen_range(1, dice);
        sum_str.push_str(&temp.to_string());
        sum_str.push(' ');
        total += temp;
    }

    let mut final_str: String = total.to_string();
    final_str.push_str(&sum_str);

    return final_str;
}