Wider more aggresive tires for Giamt Roam 1
 

I am 90% road bike rider but recently bought a new Giant Roam 1 "adventure" bike for urban and mid level off road trails. This bike is great in that it has many mountain bike features and even has Kenda 40mm side studded tires. What I really wan though is a tire even wider for the 700c rims. Something at least 45mm with mountain bike tire type treads (knobby all the way around). I have not been any to find anything on line better that the Kenda's already on it. Can anyone suggest such a tire?
Thanks.