Handle the declaration of all source code repositories in your base build file, and you don't have to worry about declaring them in any child modules. The code below would go at the top of your build.gradle, in your 'base' or 'top' build.gradle file. You don't have to add anything to child modules. You will get full repository source retrieval.

Gradle handle repos

subprojects {
    buildscript {
        repositories {
            mavenCentral()
            maven {
                url "https://oss.sonatype.org/content/repositories/snapshots"
            }
            maven {
                url "https://github.com/novoda/public-mvn-repo/raw/master/releases"
            }
        }
    }

    repositories {
        mavenCentral()
        maven {
            url "https://oss.sonatype.org/content/repositories/snapshots"
        }
        maven {
            url "https://github.com/novoda/public-mvn-repo/raw/master/releases"
        }
    }
}

-- MyProject
   build.gradle   << ADD HERE
  -- MyModule1
     build.gradle
  -- MyModule2
     build.gradle
     -- MySubSubModule1
        build.gradle
  -- MyModule3
     build.gradle