You can create .dockerignore in your root directory and add

microservice1/
microservice2/
microservice3/

to it, just like .gitignore does during tracking files, docker will ignore these folders/files during the build.

Update

You can include docker-compose.yml file in your root directory, look at docker-compose for all the options, such as setting environment, running a specific command, etc, that you can use during the build process.

version: "3"
services:
  microservice1:
    build:
      context: .
      dockerfile: ./microservice1/Dockerfile
    volumes:
      - "./path/to/share:/path/to/mount/on/container"
    ports:
      - "<host>:<container>"
    links:
      - rootservice # defines a dns record in /etc/hosts to point to rootservice
  microservice2:
    build:
      context: .
      dockerfile: ./microservice2/Dockerfile
    volumes:
      - "./path/to/share:/path/to/mount/on/container"
    ports:
      - "<host>:<container>"
    links:
      - rootservice # defines a dns record in /etc/hosts to point to rootservice
      - microservice1
  rootservice:
    build:
      context: .
      dockerfile: ./Dockerfile
    volumes:
      - "./path/to/share:/path/to/mount/on/container"
    ports:
      - "<host>:<container>"
    depends_on:
      - microservice1
      - microservice2
    ports:
      - "<host1>:<container1>"
      - "<host2>:<container2>"

This will be your build recipe for your microservices, you can now run docker-compose build to build all your images.