rails デフォルトのform_withのメソッドがgetになってしまう

Question

プログラミング初学者です。
rails 6を用いて、DM機能がついたアプリケーションを開発しているのですが、form_withのメソッドについてわからないことがあります。
form_withはメソッドのデフォルトの値がpostだと思うのですが、roomを新しく作るために作ったform_withのメソッドがなぜかgetになってしまい、下記のエラーが出てしまいます。

No route matches [GET] "/rooms"

以下が関係していると考えているコードになります。

app/views/users/show.html.erb

<% provide(:title, @user.name) %>
<div class="row">
  <aside class="col-md-4">
    <section class="user_info">
      <h1>
        <%= gravatar_for @user %>
        <%= @user.name %>
        <% if @user.id == current_user.id %>

        <% else %>
          <% if @is_room == true %>
            <%= link_to "チャットへ", room_path %>
          <% else %>
            <%= form_with(model: @room, local: true) do |f| %>
              <%= fields_for @entry do |e| %>
                <%= e.hidden_field :user_id, value: @user.id %>
              <% end %>
              <%= f.submit "チャットを始める"%>
            <% end %>
          <% end %>
        <% end %>
      </h1>
    </section>
    <section class="stats">
      <%= render 'shared/stats' %>
    </section>
  </aside>
  <div class="col-md-8">
    <%= render 'follow_form' if logged_in? %>
    <% if @user.microposts.any? %>
      <h3>投稿数(<%= @user.microposts.count %>)</h3>
      <ol class="microposts">
        <%= render @microposts %>
      </ol>
      <%= will_paginate @microposts %>
    <% end %>
  </div>
</div>

app/controllers/users_controller.erb

class UsersController < ApplicationController
  before_action :logged_in_user, only: [:index, :edit, :update, :destroy,
                                        :following, :followers]
  before_action :correct_user, only: [:edit, :update]
  before_action :admin_user, only: :destroy
  
  def index
    @users = User.paginate(page: params[:page])
    @search = User.ransack(params[:q])
  end
  
  def show
    @user = User.find(params[:id])
    @microposts = @user.microposts.paginate(page: params[:page])
    @current_user_entry = Entry.where(user_id: current_user.id)
    @user_entry = Entry.where(user_id: @user.id)
    unless @user.id == current_user.id
      @current_user_entry.each do |cu|
        @user_entry.each do |u|
          if cu.room_id == u.room_id then
            @is_room = true
            @room_id = cu.room_id
          end
        end
      end
      if @is_room
      else
        @room = Room.new
        @entry = Entry.new
      end
    end
  end
  
  def new
    @user = User.new
  end
  
  def create
    @user = User.new(user_params)
    if @user.save
      @user.send_activation_email
      flash[:info] = "メールが送信されました。アカウントを認証してください。"
      redirect_to root_url
    else
      render 'new'
    end
  end
  
  def edit
    @user = User.find(params[:id])
  end
  
  def update
    @user = User.find(params[:id])
    if @user.update(user_params)
      flash[:success] = "アカウント編集が完了しました"
      redirect_to @user
    else
      render 'edit'
    end
  end
  
  def destroy
    @user = User.find(params[:id])
    @user.destroy
    flash[:success] = "#{@user.name}さんを削除しました"
    redirect_to users_url
  end
  
  def search
    @search = User.ransack(params[:q])
    @search_users = @search.result.page(params[:page])
  end
  
  def following
    @title = "Following"
    @user  = User.find(params[:id])
    @users = @user.following.paginate(page: params[:page])
    render 'show_follow'
  end

  def followers
    @title = "Followers"
    @user  = User.find(params[:id])
    @users = @user.followers.paginate(page: params[:page])
    render 'show_follow'
  end

  private
  
    def user_params
      params.require(:user).permit(:name, :email, :password, 
                                    :password_confirmation)
    end
  
    def correct_user
      @user = User.find(params[:id])
      redirect_to(root_url) unless current_user?(@user)
    end
    
    def admin_user
      redirect_to(root_url) unless current_user.admin?
    end
  
end

config/routes.rb

Rails.application.routes.draw do
  
  get 'password_resets/new'
  get 'password_resets/edit'
  get 'sessions/new'
  root 'static_pages#home'
  get '/about', to:'static_pages#about'
  get '/contact', to:'static_pages#contact'
  get '/signup', to:'users#new'
  get '/login', to:'sessions#new'
  post '/login', to:'sessions#create'
  delete '/logout', to:'sessions#destroy'
  get '/micropost_search', to:'microposts#search'
  get '/user_search', to:'users#search'

  
  resources :users do
    member do
      get :following, :followers
    end
  end

  resources :users
  resources :account_activations, only: [:edit]
  resources :password_resets,     only: [:new, :create, :edit, :update]
  resources :microposts,          only: [:create, :destroy]
  resources :relationships,       only: [:create, :destroy]
  resources :messages,            only: [:create]
  resources :rooms,               only: [:create, :show]
end

以下が参考にした記事になります。
https://qiita.com/nojinoji/items/2b3f8309a31cc6d88d03
ご教授お願いいたします。