Hi Roger,
To disable the Google calls for Website pages I performed the following steps:
1) Clone your current template if using a predefined one in which you do not have wright permissions (in our case we used the Growth template which I cloned to my own version)
2) Edit the fields.json file and remove the “font_set”: “GOOGLE” parts (including the parameter “load_external_fonts” with value “false” did not work for me).
Before:
"label": "Primary",
"name": "primary",
"type": "font",
"visibility": {
"hidden_subfields": {
"bold": true,
"italic": true,
"size": true,
"underline": true
}
},
"default": {
"color": "#231f20",
"fallback": "sans-serif",
"font": "Montserrat",
"font_set": "GOOGLE",
"variant": "400"
}
After:
"label": "Primary",
"name": "primary",
"type": "font",
"visibility": {
"hidden_subfields": {
"bold": true,
"italic": true,
"size": true,
"underline": true
}
},
"default": {
"color": "#333333",
"fallback": "sans-serif",
"font": "Roboto",
"variant": "300"
}
I changed the values for my primary and secondary fonts in the fields.json file, all other definitions (e.g. H1) then only have references to one of those two.
3) As I had previously manually set the different font values in the design settings via web editor to a Google font I had to “clean” those definitions as well.
Thus, I ensured that my fields.json contains all font definitions as needed (Roboto + specific styles) and could then set the design settings back to default (I took me some time to understand that this is necessary in addition to point 2 as your current setup otherwise contains again the “font_set”: “GOOGLE” somewhere).
4) To store the required local font Roboto locally, I used the fantastic tool of Mario Ranftl here to download the fonts and get required CSS definitions.
Then I uploaded the fonts via Hubspot’s file manager to a new folder “fonts”.
I created a css file “local_fonts.css” in the Design Manager and simply inserted the presiouly genereted css definitions there.
/* roboto-100 - latin */
@font-face {
font-family: 'Roboto';
font-style: normal;
font-weight: 100;
src: url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.eot'); /* IE9 Compat Modes */
src: local(''),
url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.woff2') format('woff2'), /* Super Modern Browsers */
url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.woff') format('woff'), /* Modern Browsers */
url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.ttf') format('truetype'), /* Safari, Android, iOS */
url('https://19492497.fs1.hubspotusercontent-na1.net/hubfs/19492497/fonts/roboto-v30-latin-100.svg#Roboto') format('svg'); /* Legacy iOS */
}
...
Now I had to ensure that this file gets loaded for all pages, which can be ensured by including it in the HTML header (setting for all Website pages in your global configuration):
<style type="text/css">
@import url('https:{{ get_asset_url('/local_fonts.css') }}');
</style>
So - that’s it for your Website pages 
BUT: There is currently no way for Starter customers of Hubspot to have such a legally safe way also for the Landing Pages! LPs that are based on one of the standard templates (and you cannot do otherwise in the Starter Package) will always call Google APIs (confirmed to me by Hubspot support).
As this is currently against current verdicts in Germany and Austria, I created the following Hubspot request to have a lawful solution: https://community.hubspot.com/t5/HubSpot-Ideas/Provide-Landing-Page-template-without-default-Google-Font/idi-p/685609
Would be great if you could support this request!
And Hubspot Support Team: I cannot stress this enough but this whole setup is a legal topic, not some feature request. If you have a legal support team, I’m happy to provide more insights to get this issue solved for you and your customers 
All the best
Sebastian